Interview: Andrew Barrow, author

"THERE'S a theory that writing is a tidying up process. This was unfinished business. I had three suitcases filled with my brother's letters, writing and drawings, and it was time to collect and arrange my thoughts."

Andrew Barrow is describing the genesis of his ninth book, Animal Magic, a biography of his younger brother Jonathan, who was killed in a car accident, along with his fiance, Anita Fielding, on 5 April, 1970, when he was 22. They died only days before their wedding would have been celebrated at Brompton Oratory. Wedding guests found themselves attending a funeral, instead.

Spookily, among Jonathan's effects was a manuscript for his novel The Queue, in which, "road accidents, especially head-on collisions, feature often, and in which he had predicted and described his own violent death in excruciating semi-comic detail. On the page still in the typewriter he had with him on that fatal weekend he had even addressed the idea of a wedding being replaced by a funeral."

Andrew and Jonathan were the youngest of five brothers, and exceptionally close. They thrived on complex in-jokes, and wrote to one another under the names of people in the news, acquaintances and pets. The pair had an intense connection, especially in the years before Andrew joined his brothers at Harrow, when he was still at home with the animals and his mother for company.

"I used as a footnote a remark from Barry Humphries, who said that 'the best jokes are often understood by only one other person," Barrow says. "You could go further and say the best jokes are only understood by one's self, sometimes. There's nothing funnier than somebody laughing to themselves when they're in the bath."

Humour still binds the surviving brothers together, He says. "We're a very united and humour-based family and we all tease each other a lot and make jokes about each other behind our backs, as well. That's normal in a happy family. Our father encouraged it, because he was a great clown, and was always making jokingly disparaging remarks about his different children."

But Jonathan's humour was also a distancing device, one that, as he got older, he relied on to keep his worshipping older brother at a remove. When he travelled, for instance, his letters home weren't about sights seen and people met, but fanciful re-workings of family history. "Humour may have been a smokescreen. Our older brother sometimes accused Jonathan of being a bad communicator because he used jokes all the time. I know that's a famous strategy Englishmen use to avoid intimacy. I tend to believe that there's nothing ruder than politeness. It's saying, 'I don't want to know you.' "

Barrow did want to know his brother even better, so using The Queue as his map, he retraced his brother's past, and by extension, his own. From the extracts used throughout this book, the novel seems chaotic, daft, full of scatological humour and surreal situations. A central character, Mary, is an alcoholic, promiscuous dachshund. Barrow tells me Mary is the repository of all the love in the novel, and thus represents both Jonathan's fiance and an indigent, alcoholic, former schoolmaster - the last in a series of anarchic individuals Jonathan took up with - called Mr Grant.

Neither Andrew nor Jonathan attended university after Harrow. Throughout the 1960s, they shared various London flats, often homing back to elder brother Julian's studio in Chelsea, often left vacant while he travelled. Jonathan initially worked in hotels, including Claridge's, while Andrew tried his hand at stand-up. Both wound up working in advertising, though Jonathan swiftly eclipsed Andrew, landing a copywriting job with Ogilvy & Mather around the time his brother was getting sacked by the London Press Agency. Jonathan's social life was equally stellar and included a twirl through the debutante set, while Andrew floundered with the opposite sex.

"He was far more spontaneous and gifted than me," says Barrow. "The word 'upstaged' is possibly too serious somehow. He was worried about me, I think."

For all his gifts, Jonathan had a dark side, and kept secrets so well even now Andrew finds himself asking questions. "I still wonder, could he have hoaxed it? Could the whole thing be a fake and he suddenly walks into the room? Because I still can't quite believe it. In those first few months I was sustained by the idea he was still here."

I find this intriguing because at times Animal Magic is so surreal, and the boundaries between the brothers so blurry, that I wondered if it wasn't a wheeze. Could Jonathan be Andrew's invention? Even after Googling proved me wrong, doubts nagged. Barrow says I'm not the first to suggest this, though it's clear, sitting with him now, that Jonathan was real and is still much missed.

"I am a natural Boswell person, fascinated by other people," says Barrow. "About six of my books have been drawn from observation and personal experiences, including one novel about my father. What I like to think about Animal Magic, and The Queue, is that they would be of actual comfort to someone who lost a beloved friend or relation or child. Somehow it's a sort of magic carpet." With this, Barrow falters, then says, "I'm feeling quite emotional now. When I started rereading The Queue I felt it was a magic carpet. When I get on to it I fear nothing, not even death itself. Somehow it's immensely uplifting."

• The Queue will be published in a new edition in May by CB Editions. Animal Magic is out now from Jonathan Cape, 18.99.