‘I just think she’s a bit passive-aggressive,’ said the woman to her friend. ‘In a very sweet way. D’you know what I mean?’

This is so much the sort of thing you hear on the Heath that I couldn’t help smiling, straight from Stella’s funeral though I was, standing aside to let them past me on to the pavement. Even five minutes later, almost at the ponds, I’m smiling, but that could be simple relief at being outside in some November sun.

The thing about a circular walk is that you end up where you started—except, of course, that you don’t. My usual round trip removes me neatly from the fetid staffroom lunch hour, conveniently located as the school is on the very edge of the Heath. And as Head of Science I’m usually able to keep at least two lunch hours a week free by arranging as many of the departmental meetings and astronomy clubs and so on as I possibly can to take place after school.

Because I know exactly how long I have—quick glance at my watch, fifty-three minutes left—and exactly how long it takes, I can afford to let my mind off the lead. Look at the sparkle of that dog’s urine against the dark green of the laurel, and its wolfish cocked leg. In the space of an hour I know I can walk my way back to some sort of balance after my morning-off’s farewell distress before launching into sexual reproduction with Year Ten at five past two.

When the sun flares out like this, heatless and long-shadowed, the tree trunks go floodlit and even the puddles in the mud hold flashing blue snapshots of the sky. You walk past people who are so full of their lives and thoughts and talk about others, so absorbed in exchanging human information, that often their gaze stays abstractedly on the path and their legs are moving mechanically. But their dogs frisk around, arabesques of pink tongues airing in their broadly smiling jaws. They bound off after squirrels or seagulls, they bark, rowrowrow, into the sunshine, and there is no idea anywhere of what comes next.

This walk is always the same but different, thanks to the light, the time of year, the temperature and so on. Its sameness allows me to sink back into my thoughts as I swing along, while on the other hand I know and observe at some level that nothing is ever exactly the same as it was before.

It’s reminding me of that card game my grandfather taught me, Clock Patience, this circuit, today. I’m treading the round face of a twelve-hour clock. Time is getting to be a bit of an obsession but then I suppose that’s only natural in my condition. So, it’s a waiting game, Clock Patience. You deal the fifty-two cards in the pack, one for each week of the year, face down into a circle of twelve, January to December, and there is your old-fashioned clock face. I didn’t find out till last week so that’s something else to get used to. Stella would have been interested. Fascinated. The queen is at the top, at twelve o’clock, while ace is low at one.

Forty-nine minutes left. From that hill up there to my right it’s possible to see for miles, all over London, and on a clear day I’m pretty sure I can pinpoint my road in Dalston. A skipper on the Thames looked up here at the northern heights three centuries ago and exclaimed at how even though it was midsummer the hills were capped with snow. All the Heath’s low trees and bushes were festooned with clean shirts and smocks hung out to dry, white on green, this being where London’s laundry was done.

So you deal the first twelve cards face down in the shape of a clock face, then the thirteenth goes, also face down, into the middle. Do this three times more and you end up with four cards on every numeral and four in a line across the clock.

As I overtake an elderly couple dawdling towards the ponds, these words drift into my ears—‘…terrible pain. Appalling. They’ve tried this and that but nothing seems to help. Disgusting…’ The words float after me even though I speed up and leave the two of them like tortoises on the path behind me.

Start by lifting one of the four central cards. Is it a three of hearts? Slide it face up under the little pile at three o’clock, and help yourself to the top card there. Ten of spades? Go to ten o’clock and repeat the procedure. Ah, but when you turn up a king, the game gains pace. The king flies to the centre of the clock and lies face upwards. You lift his downturned neighbour and continue. Nearly always the kings beat the clock—they glare up at you from their completed gang before you have run your course, four scowling tyrants. But occasionally you get the full clock out before that happens, every hour completed; and that’s very satisfying.

‘Patience is more of a woman’s card game,’ said Aidan, who prefers poker. ‘The secretaries at work got hooked on computer solitaire. We had to get the IT department to erase it from the memories.’

We were lying in bed at the time.

‘Have you noticed how on rush-hour trains,’ I countered, ‘A seated man will open up his laptop in the middle of the general crush and you’ll think, He must have important work to do. Then you peep round the edge of the screen and he’s playing a game of exploding spaceships.’

I don’t know when I should tell him about this latest development. Pregnancy. Or even, whether.

One thing the doctor asked my grandfather to do early on, before his diagnosis, was to draw a simple clock face on a piece of paper and then sketch in the hands at five past ten. He couldn’t do it. I was there. His pencil seemed to run away with him. His clock had wavy edges, it had gone into meltdown, the numerals were dropping off all over the place and the whole thing was a portrait of disintegration.

Forty-five minutes. I can’t believe my body has lasted this long, said Stella the last time I visited her in her flat. When you think (she said), more than ninety years, it seems quite incredible. She had few teeth, three or four perhaps, and didn’t seem to mind this, although one of them came out in her sandwich that day while we were having lunch, which gave us both a shudder of horror. When she had the first of her funny turns and I visited her in hospital, she said, ‘I don’t care what’s wrong with me. Either they put it right or not. But what’s the point? Just to go on and on?’

For some reason the fact that she was ninety-three when she died and that her body was worn out did not make her death any more acceptable to this morning’s congregation. The church was rocking with indignant stifled sobs at the sight of the coffin in front of the altar, and her old body in it. She had no children but hundreds of friends. Her declared line had always been that since death is unknowable it’s simply not worth thinking about. She didn’t seem to derive much comfort from this at the end, though.

Prolongation of morbidity is what they’re calling this new lease of life after seventy. I turned to the sharp-looking woman brushing away tears beside me in the pew this morning, and said, ‘You’d think it would be easier on both sides to say goodbye; but ninety-three or not, it isn’t.’

‘That’s why I won’t allow myself to befriend old people any more,’ said my sharp neighbour. ‘I can’t afford to invest my time and emotion in them when the outcome’s inevitable.’

‘That’s hard!’ I exclaimed.

‘So’s grief,’ she growled. ‘Don’t give me grief. I’m not volunteering for it any more.’

Look at these benches, inscribed with the dates of the various dear departed, positioned at the side of the path so the living can rest on the dead and enjoy the view. There seems to be a new one every time I go for a walk. They’re the modern version of a headstone or a sarcophagus, david ford—a kindly man and a good citizen. How distant he must have been from the rest, to have this as his epitaph. Or here, equally depressing, marjorie smith—her life was devotion to others. We all know what that means.

The sharp woman this morning, she had a whiff of therapy-speak about her. What she said, the way she said it, reminded me of my father in some way. Let the past go, he declares; what’s the point in raking over the past, chewing over old news. As my mother would say, How convenient. And when, precisely, does the past begin, according to him? Last year? Yesterday? A minute ago?

My father, living in Toronto at the moment, has a deliberately poor memory and refuses nostalgia point-blank. There has been a refreshing lack of clutter in the various places he’s lived since leaving home when I was five. He treats his life as a picaresque adventure, sloughing off old skin and moving on, reinventing himself on a regular basis. He lives with the freshness and brutality of an infant. He can’t see the point of continuity, he feels no loyalty to the past. What he values is how he feels now. That phrase, ‘Where are we going?’, he’s allergic to it, and from the moment a woman delivers herself of those words to him she’s on the way out as far as he is concerned. Goodbye Sarah, Lauren, Anna, Phoebe and countless others, the women whom he refers to as romantic episodes.

I don’t see my life in quite the same way, though I have a certain sympathy for that nonchalant approach. Aidan, for example, likes to identify his objectives and be proactive at taking life by the scruff of the neck; whereas I prefer to nose forward instinctively, towards some dim but deeply apprehended object of desire which I can’t even put into words. He says that’s our age difference showing: I’ve got a touch of the old hippy still whereas he’s free of those sentimental tendencies. Anyway, I used to say to him, what if nothing much happens to you, or lots of different disjointed things? Does that make you any less of a person? I suppose I was being aggressive-passive.

At least I was being open, unlike Aidan who has a selective memory and failed to mention he was married. When I found out, then it was time for me to let the past go, to move on, despite his talk of leaving. I wasn’t born yesterday.

My mother could not be more different from my father. Why they married is a mystery. She is perpetually at work on weaving the story of her life; she sees herself as the central figure in her own grand tapestry. She carries her past with her like a great snail shell, burnished with high-density embellishments. She remembers every conceivable anniversary—birthdays, deaths, first kisses, operations, house moves—and most of her talk starts, ‘Do you remember?’ There is quite a lot I don’t remember, since I left home and Scotland as soon as I could, not popular with my stepfather, the Hero in her quest, her voyage-and-return after the false start that was my father. I was heavily abridged in the process. I’d be willing to bet a thousand pounds that her main concern once I tell her about the baby will be how to incorporate the role of grandmother into her carefully woven narrative. Still, Aberdeen is a long way off.

I’m finding more and more when I meet new people that, within minutes of saying hello, they’re laying themselves out in front of me like scientific diagrams which they then explain—complex specimens, analysed and summed up in their own words. They talk about their past in great detail, they tell me their story, and then—this is what passes for intimacy now—they ask me to tell them mine. I have tried. But I can’t. It seems cooked up, that sort of story. And how could it ever be more than the current version? It makes me feel, No that’s not it and that’s not it, as soon as I’ve said something. Perhaps I’m my father’s daughter after all. It’s not that I’m particularly secretive—it’s more to do with whatever it is in us that objects to being photographed.

And here’s the oldest jogger I’ve seen for a while, barely moving, white-bearded—look, I’m going faster than him even at walking pace. It’s hard not to see a bony figure at his shoulder, a figure with a scythe.

I was on the tube this morning minding my own business when I realized that the old fellow standing beside me—not quite Zimmer-frame, but bald, paunchy, in his early seventies—was giving me the eye. I looked back over my shoulder instinctively. Then I realized that it was me he was eyeing and couldn’t restrain a shocked snort of laughter. The parameters shift once you’re past forty, it seems, when it comes to the dance of wanting and being wanted. Though that was always very good with Aidan, whatever else was wrong between us, and he’s seven years younger than me.

You would think that a science teacher and tutor of sex ed would know how not to get pregnant. You would think so. Once again it was to do with my age. My GP noticed that I’d just had another birthday and advised me to stop taking the Pill. It was time to give my system a rest, she suggested, time to get back in touch with my natural cycle again now that I was so much less fertile because of the years. There are other methods of contraception far more natural, she continued, and far less invasive than stroke-inducing daily doses of oestrogen and progestogen. She sent me off to a natural family-planning guru.

I learned to chart the months, colouring my safe days in blue and my fertile days in red, in advance, thanks to the clockwork regularity of my cycle. It was pretty much half-and-half, with the most dangerous time from day thirteen to day seventeen, day one being the first day of my period. I took my temperature with a digital thermometer every morning and believed that I was safe once it had risen by 0.2 degrees from a previous low temperature for three days in a row. The onset of a glossy albuminous secretion, though, meant I had to be on red alert.

Emboldened by contact with my own inner calendar, its individual ebb and flow, I took a pair of compasses and made a circular chart for each monthly revolution on tracing paper, with several inner circles all marked with the days of my private month, recording dates of orgasm, vivid dreams, time of ovulation, phases of the moon and so on. I was steadier and more pedestrian during the first half of my inner month, I noticed—and more thin-skinned, clever and volatile in the fortnight before my period.

When after several months I placed the translucent sheets of tracing paper on top of each other, I was able to see both the regularly repeated events and also the slight variations over time as a wheeling overlap, so that looking back down the past year was like gazing into a helix with seashell striations.

‘My cycle seems rather disturbed,’ I said to the Wise Woman at one of our consultations.

‘Two teaspoons of honey daily should regularize that,’ she said. And I nodded and smiled. No kidding. Me, with a biology degree from a good university and a keen interest in neuroscience. Then, of course, three weeks after saying goodbye forever to Aidan, I found I was pregnant. Talk about the biological clock.

Thirty-six minutes left. See the sun on the bark of this sweet-chestnut tree, and how it lights up the edges of these spiralling wrinkled grooves. Our brain cortex looks like wet tree bark, as I was telling Year Eleven only yesterday. This expansive outer layer with its hundred billion nerve cells has to contract itself into tightly concertinaed ripples and ridges, it has to pleat and fold back on itself in order to pack down far enough to fit inside the skull.

It’s hard to think of Stella this morning in her coffin, her bones, her skull with the brain annihilated. She could remember ninety years ago, as many nonagenarians can, as though it were yesterday; but—unusual, this—she could also remember yesterday. That is a great thing in extreme old age, to be both near- and far-sighted. Once I asked her what was her earliest memory, and she thought it might have been when she was one or possibly two, sitting outside the post office in her pram on a snowy day. She was watching the boy in the pram on the other side of the doorway as he howled and howled—’And I thought, “Oh do be quiet! They’re coming back, you know. It’s really ridiculous to make a noise like that. They haven’t left us here forever.” He was wearing a white fur bonnet which I wanted for myself.’

This memory of hers sent some messenger running in my brain, zigzagging along corridors and byways of the mind, and triggered the retrieval of my own earliest memory, which she heard with a hoot of incredulity. I was standing outside my parents’ bedroom door, and for the first time felt flood over me the realization that they were not part of me. They were separate. And I thought of my own selfish demands, and wanted to go into them and say how sorry I was for being a burden to them and how considerate they would find me now that I had realized I was not part of them. The bedroom door was tall as a tree in front of me.

‘Very guilty,’ I told Stella. ‘I feel guilty generally. Don’t you?’

She paused and we both waited to see what she would come up with. Talking to her was like mackerel fishing, the short wait and then the flash of silver.

‘I don’t feel guilty enough?’ she said, with emphasis, at last.

When her doorbell rang, she would open the front-room window of her first-floor flat and let down a fishing line with a key attached to the end of it where the hook would otherwise have been. That way her visitors could unlock the front door and let themselves in, saving her the stairs.

She listened with interest while I tried to describe the latest theories about memory, how they now think that when you try to remember something you are not going to your mental library to take a memory-book off the shelf or to play back a memory-videotape. No, you are remembering the original memory; you are reconstructing that memory. The more frequently you chase a particular memory and reconstruct it, the more firmly established in the brain that memory track becomes.

This short cut I’ve just taken—thirty-one minutes, I’m watching the time—at first it was nothing but that the grass had been walked on once or twice; but it’s obviously been trodden over again and again, hundreds of times, and has become an established path. Repetition—repeated reconstruction of the memory—strengthens it.

‘So, Stella,’ I said, ‘You remember that fur bonnet from ninety years ago because you’ve remembered it so often that by now it’s an established right of way, it’s on all your maps.’

‘I am not aware of having called up that memory more than once or twice,’ said Stella. ‘In fact I could have sworn it appeared for the first time last week. But you may be right.’

Occasional Bentleys used to glide down our mean street and disgorge a superannuated star or two—a fabled ex-Orsino, a yesteryear Hamlet. Stella had been a well-known actress, she had travelled the world with various theatre companies, she had never married; nor apparently had she ever made much money, for here she was in extreme old age living in a rented room on next to nothing. She was still working, for heaven’s sake. Three times a week she would creep painfully down the stairs a step at a time, allowing a good twenty minutes for the descent, then wait for the bus to take her into Gower Street, where she introduced her students to Beatrice and Imogen and Portia and the traditional heartbeat of the iambic pentameter. She remained undimmed, without any of the usual inward-turning self-protective solipsism, open like a Shakespearean heroine to grief and chance and friendship even in her tenth decade.

If it is true that each established memory makes a track, a starry synaptic trail in the brain, and that every time we return to (or as they insist, reconstruct) that particular constellation of memory, we strengthen it, then so is the following: Stella’s billion lucent constellations may have been extinguished at her death, but she herself has become part of my own brain galaxy, and part of the nebulous clusters of all her myriad friends. Every time I remember Stella, I’ll be etching her deeper into myself, my cells, my memory.

Twenty-nine minutes until I’m due back at school. That staffroom yesterday was like a rest home for the elderly. The young ones had all gone off to leap around at some staff-pupil netball match, leaving the over-thirties to spread out with their sandwiches. I sat marking at a table near to where Max, Head of Maths, was chatting with Lower-School-History Peter and the new Geography woman.

‘It’s on the tip of my tongue,’ said Max, his eyes locking hungrily on to Peter’s. ‘You know, the one that looks like…’

‘In Year Eight?’ said Peter.

‘Bloody hell, I’ve got that thing,’ groaned Max, ‘You know, that disease, what the hell’s it called, where you can’t remember anything…’

‘No you haven’t!’ snapped Peter. He fancies him.

‘I went to get some money out on Sunday,’ he fretted. ‘I stood in the queue for the cash machine for ten minutes then when it was my turn I couldn’t remember my PIN number. I’m Head of Maths, for pity’s sake. So I tapped in 1989—in case I’d used my memorable date, because that’s it—but apparently I hadn’t because the machine then swallowed my card.’

‘You read about people being tortured for their PIN number,’ said the new Geography woman—what is her name—‘Well, they could torture me to within an inch of my life and I still wouldn’t know it. I’d be dead and they still wouldn’t have the money.’

‘What happened in 1989?’ asked Peter keenly.

‘Arsenal beat Liverpool 2-0 at Anfield,’ said Max.

‘Did they?’ said Peter.

‘You’re not into football, then,’ said Max as he turned to the crossword, shaking out his newspaper, and Peter’s face fell.

It reminded me of that scene in the restaurant last time I was out for a meal with Aidan. The couple at the neighbouring table were gaping at each other wordlessly, silent with frustration. Then he electrified everyone within earshot by softly howling, ‘It’s gone, it’s gone.’ I thought he’d swallowed a tooth, an expensive crown. His expression seemed to bear this out—anguish and a mute plea for silence. But no—it was merely that he had forgotten what he was halfway through saying. He was having a senior moment.

I’ve always had a very good memory. It used to be that any word I wanted would fly to me like a bird; I’d put my hand up and pluck it out of the air. Effortless. Gratifying. Facts, too, came when called, and when someone gave me their phone number I would be able to hold it in my head till later when I had a pen—even several hours later.

Thanks to this, I never had any trouble with exams, unlike my GP cousin who spent her years at medical school paddling round frantically in a sea of mnemonics. ‘Two Zulus Buggered My Cat,’ she’d say. ‘Test me, I’ve got to learn the branches of the facial nerve.’ And what was the one she found so hideously embarrassing? See if I can remember. It was the one for the cranial nerves.

Not that she’s prudish, but she was in a predominantly male class of twenty-two-year-olds at the time, and that’s her name—Veronica.

The minute I hit forty, I lost that instant recall. I had to wait for the right cue, listen to the cogs grinding, before the word or fact would come to me. Your brain cells are dying off, Aidan would taunt.

Even so, I sometimes think my memory is too good. I don’t forget enough. I wish I could forget him. It’s all a question of emotional metabolism, whether you’re happy or not. You devour new experience, you digest and absorb what will be nourishing, you let the rest go. And if you can’t shed waste matter, you’ll grow costive and gloomy and dyspeptic. My mother always says she can forgive (with a virtuous sigh); but she can never forget (with a beady look). She is mistaken in her pride over this. Not to be able to forget is a curse. I read somewhere a story that haunted me, about a young man, not particularly clever or remarkable in any way except that he remembered everything that he had ever seen or heard. The government of whatever country it was he lived in grew interested, thinking this might be useful to them, but nothing came of it. The man grew desperate, writing out sheets of total recall and then setting fire to them in the hope that seeing them go up in flames would raze them from his mind. Nothing worked. He was a sea of unfiltered memories. He went mad.

Max is worried that forgetting his PIN number is the first step to losing his mind but really his only problem is that he knows too much. How old is he? Near retirement, anyway. Twenty years older than me. After a certain age your hard disk is much fuller than it’s ever been, thanks to the build-up of the years. Mine has certainly started refusing to register anything it doesn’t regard as essential—I frequently find myself walking back down the road now to check I’ve locked the front door behind me. Your internal organs stop self-renewing at a certain point, and at the same time your mind begins to change its old promiscuous habits in the interests of managing what it’s already got.

I sometimes taunt Max with the crossword if I’m sitting near him in the staffroom in the lunch hour. ‘It’s on the tip of my tongue,’ he moans. Last week there was a brilliant clue, tailor-made for a mathematician too—‘Caring, calm, direct—New Man’s sixty-third year. (5,11; 9 Across and 3 Down).’ He rolled his eyes and scowled and moaned, followed various trails up blind alleys, barked with exasperation, and his mind ran around all over the place following various scents. It was interesting to observe him in the act.

Twenty-five minutes, and I’ve reached the tangled old oak near the top fence with its scores of crooked branches and thousands of sharp-angled twigs. I use trees to help me explain to my sixth-form biologists how the brain works. ‘Neurons are the brain’s thinking cells,’ I say, and they nod. ‘There are billions of neurons in everyone’s brain,’ I say, and they nod and smile. ‘And each one of these billions of neurons is fringed with thousands of fine whiskers called dendrites,’ I continue, while they start to look mildly incredulous—and who can blame them? The word dendrite comes from the Greek for tree, I tell them, and our neuron-fringing dendrites help create the brain’s forest of connectivity. Dendrites are vital messengers between neuron and neuron, they cross the little gappy synapses in between, they link our thoughts together. It’s as though several hundred thousand trees have been uprooted and had their heads pushed together from every direction—there is an enormous interlocking tangle of branches and touching twigs.

While I waited for Max as he wrestled with that clue, I could almost hear the rustle and creak of trees conferring. ‘I’ll give you another clue,’ I said. ‘You’re in it.’ But even that didn’t help him.

It’s not that my mind is going, it’s more like my long-term memory is refusing to accept any more material unless it’s really unmissable. When I was young I remembered everything because it was all new. I could remember whether I’d locked the door because I’d only locked it a few hundred times before. Now I can’t ever remember whether I’ve locked it as I’ve done it thousands of times and my memory will no longer deign to notice what is so old and stale.

My short-term memory is in fact wiping the slate clean disconcertingly often these days. Like an autocratic secretary, it decides whether to let immediate thoughts and impressions cross over into the long-term memory’s library—or whether to press the delete button on them. ‘I’ve got an enormous backlog of filing and I simply can’t allow yet more unsifted material to accumulate,’ it snaps, peering over its bifocals. ‘It’s not that there isn’t enough space—there is—but it’s got to the point where I need to sort and label carefully before shelving, or it’ll be lost forever—it’ll be in there somewhere, but unretrievable.’

The thing about my sixth formers—about all my pupils, in fact—is that it is not necessary for them to commit anything to memory. Why should they store information in their skulls when they’ve got it at their fingertips? Yet Stella’s decades of learning speeches by heart meant that when age began its long war of attrition her mind was shored up with great heaps of blank verse. I have noticed myself that if I don’t continue to learn by repetition, even just the odd phone number, then my ability to do so starts to slide away. I will not, however, be trying to learn Russian in my old age as I once promised myself. No, I’ll follow the progress of neuroscientific research, wherever it’s got to. I’ve learned from Jane Blizzard’s example that you have to find a way to graft new stuff on to old in order to make it stick.

My ex-colleague Jane had been teaching French and Latin for as long as anyone could remember. She decided when she took early retirement at fifty-five last year that she wanted to study for the three sciences at A level, and came to me for help in organizing this. Forty years ago she had not been allowed to take science at her all-girls school, even at a lower level, and felt this was a block of ignorance she wanted to melt. She’s clever, and passed the three A levels with flying colours, but to her horror discovered a few months later that all her newly acquired knowledge had trickled away. She had not been able to attach it to anything she already knew, and her long-term memory had refused to retain it.

As I overtake a couple of pram-pushing mothers in their early thirties, I hear, ‘Her feet were facing the wrong way.’ Would this mean anything to a girl of seventeen? Or to a man of sixty-three? My pupils will baulk at my pregnancy. The younger ones will find it positively disgusting. I speed up and pass two older women, late fifties perhaps, free of make-up, wrapped in a jumble of coloured scarves and glasses on beaded chains, escorting a couple of barrel-shaped Labradors as big as buses. ‘She was just lying on the pavement panting, refusing to move,’ one of them announces as I pass. They have moved on from the dramas of children to the life-and-death stuff of dogs. And I, I who am supposed to be somewhere between these two stages, where am I in this grand pageant? My colleagues will say to each other, So why didn’t she get rid of it?

Eighteen minutes left, and I’m making good time. If I’m lucky I might even catch Max groaning over his unsolved clues and help put him out of his misery.

It was my grandfather again who introduced me to crosswords—first the general knowledge ones, then, as I left childhood, the cryptics. He had an acrobatic mind and a generous nature. I used to stay with him and my grandmother for long stretches of the school holidays, as we liked each other’s company and my parents were otherwise involved.

When my grandfather started to forget at the age of eighty-one—by which time I had long since finished at university and was on to my second teaching job—it was not the more usual benign memory loss. It was because his short-term memory, his mind’s secretary, was being smothered and throttled by a tangle of rogue neurofibres.

Since different sorts of memory are held in different parts of the brain, the rest stayed fine for a while. He could tell me in detail about his schooldays, but not remember that his beloved dog had died the day before. It reminded me of the unsinkable Titanic with its separate compartments. In time, his long-term memory failed as well. The change was insidious and incremental, but I noticed it sharply as there would usually be several months between my visits.

Talking to someone whose short-term memory has gone is like pouring liquid into a baseless vessel. Your words go straight through without being held at all. That really is memory like a sieve. While I was digging the hole in his back garden in which to bury the dog, he stood beside me and asked what I was doing.

‘Poor Captain was run over,’ I replied, ‘So I’m digging his grave.’

‘Oh that’s terrible,’ he exclaimed, tears reddening his rheumy old eyes. ‘How terrible! How did it happen?’

I described how Captain’s body had been found at the kerbside on the corner of Blythedale Avenue, but he was examining the unravelled cuff of his cardigan by the time I’d finished.

‘What’s this hole you’re digging, then?’ he asked, a moment or two after I’d told him; and I told him again, marvelling to see new grief appear in his eyes. As often as he asked I answered, and each time his shocked sorrow about the dog was raw and fresh. How exhausting not to be able to digest your experience, to be stalled on the threshold of your own inner life. For a while he said that he was losing himself, and then he lost that.

Finding his way back into a time warp some fifty years before, he one night kicked my terrified old grandmother out of bed because, he said, his parents would be furious at finding him in bed with a stranger.

‘I’m not a stranger,’ she wept. ‘I’m your wife.’

‘You say so,’ he hissed at her, widening his eyes then narrowing them to slits. ‘But I know better.’

From then on, he was convinced that she was an impostor, a crafty con-artist who fooled everybody except himself into thinking that she was his eighty-year-old wife.

In the evenings he would start to pace up and down the length of their short hallway, muttering troubled words to himself, and after an hour or so of this he would take the kettle from the kitchen and put it in the airing cupboard on the landing, or grab a favourite needlepoint cushion from the sofa and craftily smuggle it into the microwave. He wrote impassioned incomprehensible letters in their address book, and forgot the names of the most ordinary things. I mean, really forgot them. ‘I want the thing there is to drink out of,’ he shouted when the word ‘cup’ left him. He talked intimately about his childhood to the people on the television screen. He got up to fry eggs in the middle of the night. He accused me of stealing all their tea towels.

‘I want to go home,’ he wept.

‘But you are home,’ howled my grandmother.

‘And who the hell are you?’ he demanded, glaring at her in unfeigned dismay.

But, because muscle memories are stored in quite another part of the brain, the cerebellum at the back, he was still able to sit at the piano and play Debussy’s L’ Isle joyeuse with unnerving beauty.

Thirteen minutes. It always surprises me how late in the year the leaves stay worth looking at. November gives the silver birches real glamour, a shower of gold pieces at their feet and still they keep enough to clothe them, thousands of tiny lozenge-shaped leaves quaking on their separate stems. That constant tremor made them unpopular in the village where I grew up—palsied, they called them.

Trees live for a long time, much longer than we do. Look at this oak, so enormous and ancient standing in the centre of the leaf-carpeted clearing, it must be over five hundred years old. It’s an extremely slow developer, the oak, and doesn’t produce its first acorn until it’s over sixty. Which makes me feel better about the elderly prima gravida label.

They have been known to live for a thousand years, oak trees, and there are more really old ones growing on the Heath than in the whole of France. Look at it standing stoutly here, all elbows and knees. When the weather is stormy, they put up signs round here—beware of falling limbs. It was these immensely strong and naturally angled branches, of course, which gave the Elizabethans the crucks they needed for their timber-framed houses and ships.

Stella was like seasoned timber, she stayed strong and flexible almost until the end. When she had her second stroke, three weeks after the first, she was taken to a nursing home for veterans of the stage and screen, somewhere out in Middlesex. In the residents’ lounge sat the old people who were well enough to be up. They looked oddly familiar. I glanced round and realized that I was recognizing the blurred outlines of faces I had last seen ten times the size and seventy years younger. Here were the quondam matinee idols and femmes fatales of my grandparents’ youth.

Then I went to Stella’s room. I held her strong long hand and it was a bundle of twigs in mine. There was an inky bruise to the side of her forehead. Her snowy hair had been tied in a little topknot with narrow white satin ribbon.

I talked, and talked on; I said I’d assume she understood everything—‘Squeeze my hand if you can to agree’—and felt a small pressure. I talked about Shakespeare and the weather and food and any other silly thing that came into my head. Her blue eyes gazed at me with such frustration—she couldn’t move or speak, she was locked in—that I said, ‘Patience, dear Stella. It’s the only way.’

Her face caved in on itself, a theatrical mask of grief. Her mouth turned into a dark hole round her toothless gums, a tear squeezing from her old agonized eyes, and she made a sad keening, hooting noise.

Afterwards, in the corridor, I stood and cried for a moment, and the matron gave me automatic soothing words.

‘Not to worry,’ I said. ‘I’m not even a relative. It’s just the pity of it.’

‘Yes, yes,’ she said. ‘The pity of it, to be sure. Ah but during the week I nurse on a cancer ward, and some of those patients having to leave their young families…’

I really did not want to have to think about untimely death on top of everything else, and certainly not in my condition; so I returned to the subject of Stella.

‘Walled up in a failed body,’ I said. ‘Though perhaps it would be worse to be sound in body but lost in your mind, dipping in and out of awareness of your own lost self. Which is worse?’

‘Ah well, we are not to have the choice anyway,’ she said, glancing at her watch. ‘We cannot choose when the time comes.’

The trouble is, old age has moved on. Threescore years and ten suddenly looks a bit paltry, and even having to leave at eighty would make us quite indignant these days. Sixty is now the crown of middle age. And have you noticed how ancient the parents of young children are looking? Portly, grizzled, groaning audibly as their backs creak while they lean over to guide tiny scooters and bicycles, it’s not just angst at the work-life balance that bows them down—it’s the weight of the years. Last time I stopped for a cup of tea at the cafe over by the bandstand, I saw a lovely new baby in the arms of a white-haired matriarch. Idly I anticipated the return of its mother from the Ladies and looked forward to admiring a generational triptych. Then the baby started to grizzle, and the woman I’d taken for its grandmother unbuttoned her shirt and gave it her breast. No, it’s not disgust or ridicule I felt, nothing remotely like—only, adjustment. And of course that will probably be me next year.

My baby is due early in summer, according to the dates and charts. If it arrives before July, I’ll still be forty-three. Who knows, I might be only halfway through; it’s entirely possible that I live to be eighty-six. How times change. My mother had me at thirty-two, and she will become a grandmother at seventy-five. Her mother had her at twenty-one, and became a grandmother at fifty-three. At this rate my daughter will have her own first baby at fifty-four and won’t attain grandmotherhood until she’s 119.

I’d better take out some life insurance. I hadn’t bothered until now because if I died, well, I’d be dead so I wouldn’t be able to spend it. But it has suddenly become very necessary. I can see that. Maternity leave and when to take it; childminders, nurseries, commuting against the clock; falling asleep over marking; not enough money, no trees in Dalston; the lure of Cornwall or Wales. I’ve seen it all before. But it’s possible with just the one, I’ve seen that too.

I’m not quite into the climacteric yet, that stretch from forty-five to sixty when the vital force begins to decline; or so they used to say. And a climacteric year was one that fell on an odd multiple of seven (so, seven, twenty-one, thirty-five and so on), which brings me back to my glee at that crossword clue last week, and the way I taunted old Max with it—’Caring, calm, direct—New Man’s sixty-third year. (5,11; 9 Across and 3 Down).’ Grand climacteric, of course. The grand climacteric, the sixty-third year, a critical time for men in particular.

To think that my grandfather had three more decades after that. Towards the end of his very long life—like Stella, he lived to ninety-three—it was as though he was being rewound or spooled in. He became increasingly childish, stamping his feet in tantrums, gobbling packets of jelly babies and fairy cakes, demanding to be read aloud to from The Tale of Two Bad Mice. He needed help with dressing and undressing, and with everything else. Then he became a baby again, losing his words, babbling, forgetting how to walk, lying in his cot crying. Just as he had once grown towards independence, so, with equal gradualness, he now reverted to the state of a newborn. Slowly he drifted back down that long corridor with fluttering curtains. At the very end, if you put your finger in the palm of his hand, he would grasp it, as a baby does, grab it, clutch at it. When at last he died, his memory was as spotless as it had been on the day he first came into the world.

Seven minutes left, and I’ll pause here at the home-run ash tree to pull off a bunch of keys, as children do, for old time’s sake. So ingenious, these winged seeds drying into twists which allow them to spin far from the tree in the wind; nothing if not keen to propagate. I have a particular liking for this ash tree; it’s one of my few regular photographic subjects.

I’m careful how I take photographs. I’ve noticed how you can snap away and fail to register what you’re snapping; you can take a photograph of a scene instead of looking at it and making it part of you. If you weren’t careful, you could have whole albums of the years and hardly any memories of them.

I take my camera on to the Heath, but only on the first of the month, and then I only take the same twelve photographs. That is, I stand in exactly the same twelve places each time—starting with the first bench at the ponds and ending with this ash tree—and photograph the precise same views. At the end of the year I line up the twelves in order, the February dozen beneath the January dozen and so on, and in the large resultant square the year waxes and wanes. You don’t often catch time at work like this. Aidan was quite intrigued, and soon after we met he was inspired to add a new Monday morning habit on his way to work. He left five minutes early, then paused to sit in the kiosk near the exit at Baker Street to have four of those little passport photos taken. He stuck these weekly records into a scrapbook, and after eighteen months it was nearly full. It was what I asked for in September when I found out that he already had a wife and child. He refused. So, in a rage, I took it. I was going to give it back, it belonged to him; but now of course it doesn’t belong to him in the same way any more. It’s his baby’s patrimony.

I have a feeling that this baby will be a girl. In which case, of course, I’ll call her Stella. If the dates are accurate, then she’ll be born in early summer. I might well be pushing her along this very path in a pram by then, everything green and white around us, with all the leaves out and the nettles and cow parsley six feet high.

Four minutes to go, and I’m nearly there. Walking round the Heath on days like this when there is some colour and sun, I can feel it rise in me like mercury in a thermometer, enormous deep delight in seeing these old trees with their last two dozen leaves worn like earrings, amber and yellow and crimson, and in being led off by generously lit paths powdered silver with frost. It must be some form of benign forgetfulness, this rising bubble of pleasure in my chest, at being here, now, part of the landscape and not required to do anything but exist. I feel as though I’ve won some mysterious game.

Two minutes to spare, and I’m back where I started, off the path and on to the pavement. That got the blood circulation moving. It’s not often that I beat the four scowling kings. There’s the bell. Just in time.

Photograph © verseguru