JONATHAN Rendall has suffered for his art - much, admittedly, self-inflicted. Earlier this summer, toiling on a biography of boxer Mike Tyson, he collapsed several times.

JONATHAN Rendall has suffered for his art - much, admittedly, self-inflicted. Earlier this summer, toiling on a biography of boxer Mike Tyson, he collapsed several times. It meant time in hospital and an infusion of vitamins.

In Woodbridge he nipped out to the shops and woke up nursing a bang on the head. It was severe concussion and the doctor reckoned he was lucky not to suffer bleeding on the brain.

Some years ago, writing his book Twelve Grand, his teeth turned black and the weight of his 6ft 1.5in frame dropped to under 10-stone.

Locked into a creative project, he's wont to get a bit obsessed. Alcohol flows too readily, though he says he's been good recently.

“Not eating is the killer; that is basically what caused my collapse,” he confesses. “Also, the fact I was keeping crazy hours. I got into this habit of getting up at 6am, because you work out in your head how many words you've got to do.”

Fortunately, the headaches have gone. In fact, he's feeling pretty chipper today. Publisher HarperCollins requested the Tyson epic be expanded by another 35,000 words. In return, Jonathan sought more of the advance. The money's zinged through and now £5,000-odd is metaphorically tucked in his back pocket.

But Tyson is next year's hoped-for blockbuster. Current thoughts focus on his book Garden Hopping. It exposes to public gaze his sometimes turbulent upbringing with his adoptive parents and the discovery of his birth mother more than 30 years after she gave him up. At one time she threatened to take legal action over the book, but is said to have withdrawn it.

“Probably I would put the estimate with this book on three years before we start talking again,” he half-smiles - “we” meaning his birth mother and his adoptive parents. “They all say they're not going to read it, but I know they will.”

It's a bit of a bleak journey. Jonathan's relationship with Jay, his adoptive mother, was tense. He claims the strict disciplinarian sometimes hit him when he was a boy, although he remembers his childhood as generally happy and active. He has some good times when he finds Marianne, a secretary when she gave birth to him in 1964, but there's not the normal mother-and-son history on which to build a deep relationship.

Along the way - and largely unconnected with the adoption experience - we witness the end of the author's marriage, his career hitting a rocky patch, living rough, and keeping afloat by tending to ex-pat Scots at their London club.

An Oxford graduate, he won the Somerset Maugham Award for his inside-boxing book This Bloody Mary Is The Last Thing I Own in 1998 - putting himself in the company of such luminaries as Kingsley Amis and Ted Hughes.

But life became a bit of a surreal rollercoaster ride. One minute Jonathan (in his role as manager of Colin “Sweet C” McMillan - “a strange four-year interlude”) is clinching a £250,000 fight deal with big-league promoter Frank Warren; the next, his novel Twelve Grand spawns a Channel 4 series. He has his journalism printed in national broadsheets. Then the pendulum swings and the money is running out.

He reached a stage when he couldn't clinch a fiction deal. But there was a market for personal revelation. Jonathan says Marianne had given him away, “so the least she could do was let me get something out of it”.

He's wondered if he's done the right thing - if he's sold his soul for 30 pieces of silver (or, in this case, £8,000) - but concludes he's told the truth as he remembers it, and has found the process cathartic. Besides, he reckons he comes out of it worse than anyone.

The title refers to a childhood game involving running through a series of back-gardens, leaping the fences. Jonathan feels it's an apt metaphor for the search for birth parents. The book contains several insightful letters he's written to his mums and dad, but many of them remain unsent. Why?

“I don't really know. I am going to, this week, send two letters: one to Marianne and one to Jay and John, saying basically 'I hope you appreciate there's no malice in this book and I don't want you to be hurt by it, but I am also aware you're probably steeling yourselves for its release.'”

Jonathan was eight when he found out, by chance, that he was adopted. “I can't say it was a traumatic experience. I thought it was great: two mothers!”

John and Jay had two other adopted children, Kate and Andrew. Jay, he feels, was ambitious for her family and prone to moods.

Jonathan reckons infertility is much to blame. He told the EADT. “I think she never got over that and I think, if she was honest, the reason it never really worked out with any of us was that she could never quite forgive us that we weren't hers. I truly believe that.”

Has that left its mark on him?

“I think, actually, you're quite pragmatic. My adoptive mother has many merits - she's kind to animals - but I was not what she wanted, because I wasn't her real son. I don't want to blame her for that - probably I was a right nightmare in some ways.”

His school years were rocky at times. The family moved to Greece, where John had a job selling Mills & Boon romances. The children went to boarding school in England for a while, but Kate got expelled for drug-taking; Jonathan for generally bad behaviour.

He also started taking speed. But then he got his head down. A teacher reckoned Jonathan was

Oxbridge material, and he got in at Magdalen.

He read history, felt intimidated by the atmosphere of social elitism, represented the university at boxing, and got a third-class degree. He met wife-to-be Susie (who was also adopted) in a nightclub; they married when Jonathan was 24 and she was 23, and would be together 11 years. They have three children.

He became a trainee with The Times and later was senior figure on the Independent on Sunday magazine. “I wasn't getting paid that much - well, compared to now I was - and I thought that if I carried on I'd never write books.”

Buoyed by the deal for the boxing-based book, Jonathan shifted his family to a rented farmhouse at Sweffling, between Framlingham and Saxmundham, where they stayed seven or eight years and he spend time commuting to London. He'd always liked the county when he'd visited on holiday as a boy, but reflects it was an idiotic thing to do. The smell from a pig farm meant the windows stayed closed in summer, and he says he realised far too late that his wife hated such an isolated spot.

They would later split up.

He was 34 when the adoption memoir idea arose, though he says the question of who my mother was, and what she was like, had been with him since he found out he was adopted. “So I don't think I was a fraud for writing the book.”

His biological father had been an Oxford undergraduate who initially denied paternity. Marianne had tried to return home to Devon, but her father didn't want “a bastard in the house”.

Marianne (key names have been changed in the book) had a fairly common surname, and been married several times, so it wasn't easy tracking her down. Thumbing through the phonebooks at Woodbridge library eventually pays off. “I was not obsessed,” he says. “I was just curious.”

Despite a warning from the landlord at his local pub to let sleeping dogs lie, Jonathan presses ahead and finds Marianne in Devon, where she is living with her third husband. She has two other grown-up sons. Jonathan travels down by train to see her and they got on well enough.

There are further visits to the south-west. Each time, he writes, she wants to “go on a bender” on the first night. It's a kind of family tradition, she says.

Later, when things have gone quiet on the professional front and Jonathan is effectively homeless, he rings Marianne and asks to go there. She tells him: “Well, the thing is, you only ring when you're unhappy. When you're happy, you don't bother.'” He still goes, and gets a bar job.

Although Marianne says he should stay as long as he needs, he begins to feel unwanted. Her sister, for instance, gives him a look that he interprets as: “Don't think you're really part of this family.”

There is tension about borrowing the car and leaving the lights on at night, and a row with Marianne's husband about anti-social behaviour - sparked by Jonathan urinating in a waste-bin while sleepwalking.

He finds his bags outside and a note from Marianne accusing him of being arrogant. She later appears to offer a rapprochement, but the next morning Jonathan opts to catch the early bus to Totnes.

“We were both fakes, over all of this . . .” he writes in Garden Hopping. “She had no maternal instinct. It wasn't her fault . . . That was why she'd given me away. That's why Simon and Tom didn't bother with her much; and why she didn't bother too much with them . . . And that was it. End of story.”

Not quite. They're still in touch. In one of those letters that would remain unsent, Jonathan writes: “I think we are equally culpable in a way. Me for diving in and pretending that you'd been my family all along and you for doing the same.”

He accepts he had “a totally wrong romantic vision” that being reunited with his birth mother was going to bring forth a wave of euphoria.

On reflection, he doesn't think they have much in common.

“She's a bit of a party girl. She's very much like, in looks and speech and manner, Marianne Faithfull. She's a sixties girl. And I don't think she could deal with it.”

Jonathan's never subscribed to the theory that being given away as a child can be blamed for everything bad that subsequently happens in your life, though recognises it obviously has an impact.

“Although my experiences probably haven't been ideal, I am still very much in favour of adoption, because it's a hell of a lot better than growing up in care. Once you stop being babyish and pretty, kids are very hard to place. So on balance it's good.”

He concludes in Garden Hopping: “On balance, I would have to describe the experience of finding my birth mother as destructive for all concerned. It killed off whatever vestiges of a relationship I had with Mum and put Dad in an invidious position. It stirred up deep-seated and troubling emotions in me that I didn't know I had.

“I think it hit Marianne even worse. Her friends knew about her 'lost son'. She used to talk about him late at night, they said. I think she would have been better off if I'd stayed like that, in the abstract. My actual reappearance was too much for her to cope with.”

If his brother and sisters ever asked for advice about finding their own mothers, “I think I would say what John from the White Horse said: 'Don't do it.'”

(Garden Hopping is published by Canongate, priced £9.99. ISBN 978 1 84195 596 4)

GARDEN Hopping was written in an Ipswich bedsit, where Jonathan Rendall could be close to his children - a boy and two girls now aged 10, 12 and 14.

They now live with their mum in Oxfordshire, and he admits it's a bit depressing them not being closer.

That's one thing he can't understand about Marianne, his natural mother. Even when he was down on his uppers he'd travel by public transport to snatch 40 minutes with them in a windswept park, if that was all that was on offer. “She never even tried to find me.”

Home today is a flat near Ipswich Museum, but that's about to be swapped for a flat in Newmarket, where he'll be close to his girlfriend of six years - an author herself.

What about Brian Phillips, the natural father we never get to meet in the book?

Jonathan's never seen his birth father. But he has been down to his house in an affluent village in the south-east, where he noticed how the garden was arranged.

“He's an accountant - I could have been an anti-accountant - but I just liked the way it was. There was an empty wine-glass there, and music: ragtime jazz. I just thought 'If I had a house like that, that's how I would be.'”

Jonathan's written a couple of times, without getting a reply. “I think that probably he's absolutely terrified of Marianne and thinks 'Oh, he's really in the thick with her.' Also, he might think I'm after his money, which I'm absolutely not.

“I will send him a copy of the book. What I'd do in his situation is ring me up: 'I'm glad you're all right. My wife doesn't know about you. Why don't we have lunch somewhere?' No-one has to know about it.”

He adds: “I probably have a more idealised view of him than I do of Marianne, in some senses. By her account, which admittedly has changed a few times, he was a bit of a dasher; and I know from her sister she was really sweet on him and thought 'husband'. I would like to sit down with him, like this, and just have a chat. Just be adults about it; that's all I want.”