JONATHAN: When Will was three he packed a suitcase with toys — including my teddy bear — and ran away from home. He walked about three miles along the A1 and stood at a bus stop.

I remember feeling a mixture of delight that we were finally rid of him — I was the classic jealous older sibling who had not been thrilled when a new child arrived — and rather daunted by having the police in the house. Even so, we played a lot together from very young, and I remember finding him endearing.

But I saw how he became the favoured son as soon as his incredible brain was apparent to my parents, who valued intellect enormously. There was an occasion when Will and I were talking about our childhood and I asked whether he thought our parents had had a favourite. “Absolutely,” he replied. “They preferred me.”

Will is like our father, who came from the Oxford school of debating, where he’ll argue a point whether he believes it or not, and then in the end say: “You’ve got a good point… I don’t really care.”

Home life was chaotic, because our mother was a manic-depressive given to sudden irrational violence, and our father left when I was 12. In the home it was very much every man for himself. That didn’t help bonding between me and Will. In fact, it was an explosive mix: two unsupervised, jealous brothers who were close in age. I remember a scene in the kitchen when we got into a fight and I picked up a knife and started brandishing it at him — not uncommon in our home, because our mum was forever throwing knives around. But Will managed not to really react, and this way of his would drive me crazy, because I ended up feeling humiliated.

I left home aged 16 and lived in the house of a communist Quaker woman, and I got a job. At the same time I set up the Occasional Theatre Company with Emma Thompson, Emma Freud, Matthew Freud and Patrick Spottiswoode. We put on plays together, and I particularly remember Will and I doing a comedy sketch in which we were the Kray brothers.

When he went up to Oxford he introduced me to my first wife, so I visited a lot and we were close pals then. But our lives went in different directions. When I was 18 I wanted to be a journalist, but my girlfriend persuaded me I should go into advertising as a copywriter. I hated it, and I saw Will doing cartoons for the New Statesman and City Limits and felt he had the much more rewarding life.

There was a time when we didn’t speak for quite a long while. My second wife had just gone to Australia and we were fighting a lot. I was on the phone to Will telling him about this and he made some comment like: “You should lighten up.” I was terrifically wound up and it just hit my button. We were in the middle of a conversation, and I said, “I’ll phone you back,” and hung up. But I didn’t phone back and we didn’t speak for some time. I wrote a letter every week but didn’t post them. I was really upset we weren’t speaking. Then a nephew was coming over from the States and we needed to sort out arrangements, so I had to communicate. I rang him and said: “So what were you saying again?” That was it. We carried on as ever, and it was never mentioned.

I started working on a first book, then learnt that he was doing the same thing. I felt immensely competitive and when I read The North London Book of the Dead, I thought: “I’ll never be as good as that.” So I dropped mine.

Now that I’ve established myself as a writer, doing what I want, I have no sense of competition and I genuinely feel nothing but pleasure in Will’s success. We never talk about each other’s books. However, I think he quite likes being famous, whereas I like to stride through the world not being noticed.

When my mother died in 1987 we put her ashes into a plastic bottle and took them everywhere with us, including to the solicitor for the reading of the will. She was on the mantelpiece in Will’s home for a while, and I sent her postcards and left her phone messages on his machine. We decided to bury her at Kenwood [House, on Hampstead Heath], so on a very hot day we went there. Will nicked a spade and, completely fearless, he dug a hole. I was very twitchy, thinking we’d be arrested. Then, of course, none of the ashes went into the hole but all over our trousers.

Our relationship has become very companionable and pleasurable, and if we are both in the same city we make a point of meeting.

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