This room is a converted roof space at the very top of the house and it looks south-east. I have my bed along the French window, which fills the wall, so that I can lie in it and look at the sky where the sun gets up in a variety of dusky, pinkstreaked, red-flaring or plain skies, and travels past all day, and then the moon follows soon after in all its many sizes, colours and shapes. The moon is sometimes high, sometimes low down, and may disappear for a while into the branches of the great ash tree at the bottom of the garden, which is a long London garden the width of the house.

From the balcony outside the French window I look down at gardens stretching the length of the street, some neglected, a bird-inhabited confusion, some designed and formal, some the crammed delicious tangle amateurs like me may achieve, roses, irises, lilies, clematis, all out together, but then a kind of jungle, because I am too busy to keep it tamed. In these gardens wander cats of all kinds, designer cats and moggies, and the trees are noisy with birds. I and others feed them. Last week a woodpecker and two jays visited my lower veranda to find nuts that might have been rolled into spaces between pots, overlooked by squirrels and pigeons.

A big birch tree is as tall as the roof and the ash behind it is gigantic. There are cherries, apples, pears, a blackthorn, planes, and around a great green space the size of a small airfield are trees and bushes. This green field is a reservoir — the Victorians put their water under lids of earth. Across it, if it is fine, you see over roofs to the Houses of Parliament, and down to Canary Wharf, and, looking left up a hill it is Hampstead, and if you didn’t know, you’d think it was a hill of trees with an occasional roof dotted about.

From my high window I might as well be in the country. It is quiet up here in the day and at night silent, not a sound.

Down on the pavement you could think this was a London street with houses packed up behind it. Beyond the other face of houses are playing fields and an old cemetery, so in fact this conventional city street runs between green fields and trees. No one driving along it could possibly guess the truth.

It is not on the top of a hill, but almost: the reservoir is the top. The street running up to ours is so steep that when there is snow the cars slip and slide, so it is better to drive around another way. Not long ago this was a wild green hill that people might ascend going north-west, then, after resting on a flattish place, start climbing again to the heights of Hampstead. This knot of streets was built in 1890, all at once, as one of the first commuter suburbs. In the area below the reservoir, to the south, until the First World War were fields, cows, little streams. I knew an old woman who used to take a penny bus ride on Sundays from Marble Arch to where the mill was that gave Mill Lane its name — soon to be replaced by boring flats — so she could put her feet into the streams and watch cows.

As I write leaves are spinning off the trees and the gardens seem drowned in gold and orange and green, and the grass on the reservoir is emerald green in watery sunlight.

Penelope Lively | A London View