Margrave of the Marshes, by John Peel and Sheila Ravenscroft

"You look like a man who doesn't know how to circulate," I said breezily. "I never circulate," he said. "I can't ever launch myself. It's like when I was a child at the swimming baths. Hanging onto the bars at the side of the pool for all I was worth."

"Perhaps we could circulate together?" "No," said John. "I've found that if you stay in one place, eventually everyone comes to you."

Even then, that seemed a reasonable summary of John's life at the BBC as well as the simplest way of understanding his remarkable popularity. The British like people who stay in the same place, who stick with their obsessions. They also like to believe that the enthusiasms of their favourites are self-generated rather than the result of going to college or "having the Latin". The actual obsessions don't matter too much. There's no need to be hung up on shooting stars or the mating habits of stick insects to relish Patrick Moore or David Attenborough. Neither was a temperamental inability to relish The Fall or Joy Division an impediment to regarding Peel as one of those special people who can speak from within the confines of show business and still sound like a human being.

That was what caused problems when John chose to go off-piste. As long as he was holed up in some late-night corner of the BBC playing his idiosyncratic blend of original, exciting, crazy, miserabilist, unpredictable music, all was well. But as soon as he was heard on the telly "murmuring apologetically" - Sheila Ravenscroft's perfect phrase - about the merits of fizzy drinks and tinned fruit, he was, according to some of the higher-minded guardians of his flame, beginning to "sell out". An even less favourable reaction greeted his arrival on Radio 4's Home Truths. How could a former lord of misrule even pretend to be quite so absorbed by the banalities of domestic life?

Sheila, his widow, tells us that John took such criticisms "terribly hard", even though Home Truths was "no less an accurate reflection of John than his Radio 1 shows". But isn't that always the trouble with trying to make heroes of media folk? When they don't completely honour the ideal form thrust upon them, we feel betrayed.

We now know, a year after his death, that although Peel may have suffered a dip in credibility among some old supporters, he was never abandoned by the majority of the faithful. He was already far too much in credit. His laconic tones and devious musical sensibility had been the sole night-time companions for millions of lonely students, just as his readiness to listen to unsolicited tapes had been the sole salvation for hundreds of groups.

Above all, Peel enthusiasts had been injected with quite enough of his own wry take on celebrity to know that he was unlikely to have his head too far turned by either. They knew only too well that he found the hero-worship of some of his fans as comically absurd as the showbiz pretensions of fellow DJs.

Every reader of this book will also learn that there was one other obstacle to Peel taking himself or his fame too seriously. Sheila Ravenscroft may only have accepted the biographical baton when John's unexpected death left his memoir unfinished, but she emerges as a force in her own right. She has a delicious, slightly surrealist, throwaway sense of humour, an indomitable spirit (we get fewer words on her near-fatal brain haemorrhage than on John's sadness at being blanked by Marc Bolan) and a capacity for coping with anarchic drunken musicians that borders on the heroic. She is also wonderfully free of self-pity. "We're very good in our family at fooling around during the darkest times," she writes. It's the saddest and bravest statement in an honest and intelligent book.

Laurie Taylor presents 'Thinking Allowed' on Radio 4