I was not allowed to go to the movies as a child. There was a cinema in Cowbridge Road, Cardiff, not far from my home, and just about every boy I knew spent Saturday mornings there, watching low-budget serials about cowboys and space rockets, Robin Hood and Lassie. I feel a flash of recognition, now, when I read of Proust’s young narrator gazing with longing at theatre posters on the Morris columns of Paris.

I went instead to the public library, a hundred yards away from the cinema in the same street. I probably learned more there than my friends did at the movies, but I did not appreciate that at the time. On the contrary, I was outraged by the prohibition.

We called ourselves the Fellowship, or sometimes the Church of God, but the world knew us as the Plymouth Brethren. This movement split from the Church of England in the nineteenth century. Such groups are as fissile as Trotskyites, and they splintered again and again. I was born into the Needed Truth Brethren, named after our magazine, Needed Truth.

Truth is an important word in Protestant sects. Their key text is John Bunyan’s allegory The Pilgrim’s Progress, one of whose heroes is Mr Valiant-For-Truth. Their duty is not merely to seek the truth, but to proclaim it bravely, even – or especially – in defiance of misguided orthodoxy. ‘Protestantism’ is a literal term: it was always a protest movement.

My father and his brother had married two girls who were cousins, conjoining three already large families, and almost every member of the resulting clan was in the Fellowship, including my four grandparents. It was forbidden to marry outside.

Every sect needs jargon. We did not have churches, we had halls; services were called meetings; the congregation was the assembly; the elders were overseers.

We went to meetings three times every Sunday, and sometimes on Saturday afternoons too. The adults also went on at least one weeknight. I could bear all that, but from a young age I had trouble with the sect’s strict Puritanism.

In our house there was no TV, radio or gramophone. These things were ‘worldly’ – an important term for us. I was often told: ‘Our citizenship is not of this world’, a saying which paraphrases the letter of Paul to the Philippians, in which he says: ‘Our citizenship is in heaven.’ This was interpreted to mean that we should not join political parties, trade unions, the armed forces or any kind of social club. The Fellowship paid much more attention to the petty rules of Paul than to the open-hearted wisdom of Jesus.

Another bad word was ‘pleasure’. We did not go to the theatre, concerts or sporting events. I recall being told that it was all right to go to the motor show to buy a Gospel Van, but to spend a day there just because I liked cars would be wrong, for it would be nothing but pleasure.

It was an egregious sin to enter a church of another denomination – especially another branch of the Brethren. I learned, many years later, that my father’s adolescent rebellion had taken this form. At the age of fifteen, Dad went to a meeting of the Open Brethren. Now, the distance between their beliefs and ours was the breadth of a hair. A brother from another town could take part in our meetings only if he brought with him a letter of commendation from the overseers of his assembly. The Open Brethren, by contrast, would welcome anyone who said he belonged without checking, hence their name. I know of no other difference. And yet my father got into serious trouble.