Booker Contender: 'When I found out it was cancer I was utterly stunned.'

Harry Thompson has just been named as a contender for the Booker Prize with his first novel. He is also fighting for his life. By Anthony Barnes

On a daily basis he faces some form of painful, unpleasant treatment for the inoperable lung cancer which leaves him weak and struggling for breath at the simplest task. Even eating is agony - the disease has now spread to his oesophagus.

But his chance of glory in the Man Booker Prize is a pleasing distraction from Thompson's struggle.

In an exclusive interview with The Independent on Sunday, Thompson spoke of his delight at hearing the news during the bleak struggle against illness.

"I was absolutely gobsmacked to be on the list," he said. " I hadn't even bothered looking and I didn't even know that the publisher had entered me.

"Somebody told me I was on there and I thought they had made a mistake," added the 45-year-old TV executive, who has been behind shows such as Have I Got News For You, Da Ali G Show and Harry Enfield and Chums.

"Then my girlfriend looked on the internet to double check but somehow she managed to get last year's list with Doris Lessing. Actually in my current state of health, I look rather like Doris Lessing ..."

Thompson's book, This Thing of Darkness, has taken 10 years from the first germ of the idea to publication, with three years of actual writing and research. A work of historical fiction, it examines the 19th-century voyage of the Beagle and the relationship between its captain, Robert FitzRoy - a devout Christian - and his passenger Charles Darwin, whose theory of evolution ran counter to FitzRoy's faith in the Bible.

The appearance of his illness was concurrent with the book's publication.

"I had to go to a marketing dinner to meet the book trade. That night I was fast asleep, then I suddenly woke up and felt as though I had been shot. It just came out of nowhere and I was in absolute agony. I was a foot and a half away from a table by the bed where there was some Nurofen and I couldn't even reach them. I was just in a ball of pain. I had no idea what was going on.

"Strangely, I felt fine the next day and I nearly didn't do anything about it - I felt a bit of a fraud - but I went to the doctor and had a month of tests, each of them increasingly unpleasant. At first they thought it was pleurisy. And then they thought it was TB. I'd just written this Victorian book and then I seemed to have got this Victorian disease - people were taking the piss, saying you're taking your research too far. Now, I think I'd walk a hundred miles to just have pleurisy."

Thompson was diagnosed with lung cancer three and a half months ago, after doctors found "two orange-sized tumours". Medics are trying to control the spread with weekly chemo and daily radiotherapy, but he has no idea what life span he has left.

"How long is a piece of string? But there's no point in worrying about it."

His diagnosis was even more shocking because he had never smoked in his life, ate healthily and was a slim, keen sportsman. Thompson was probably, like Roy Castle before him, susceptible to passive smoking. A cruel irony is that if he had been any less fit, the impact of the disease would have been noticeable far sooner.

"When I found out it was cancer, I was utterly stunned. It is just so surprising, so kind of irrelevant. You think this is somebody else's, there's been a mistake. This belongs to some guy who smokes 60 cigarettes a day.

"I've been in my fair share of smoky rooms - and I've had my fair share of smoky girlfriends, but they haven't got this. Nobody really knows how it happens, but maybe the fact is I am just genetically susceptible."

Thompson, who was this weekend spending time with his children who live in Edinburgh with their mother, had previously written a number of biographies since his mid-20s but wanted to get to his 40s before trying a novel.

He is now working again, writing Channel 5's first ever sitcom, which will be screened next year.

"At one point I was in hospital flat on my back with a temperature of 105 degrees and close to death [caused by an abscess related to the cancer]. Now I'm at home and moving around, getting on with work as much as possible," he said.

"I've written a small, frivolous book about cricket. It's not really the ideal follow-up to a novel, and I'd probably not have written it if I'd known I was going to be on the Booker longlist."

His book is a 20-1 shot to actually win the £50,000 Man Booker Prize, and it lines up against works by Salman Rushdie, Julian Barnes and Ian McEwan, fighting for a place on the six-strong shortlist which will be announced on 8 September.

"It is actually so much more mental effort to do a proper novel with grown-up ideas than the books I have done in the past. The novel was very highly researched. I wanted it to be as close as possible to history, and I went through thousands of pages of FitzRoy and Darwin's diaries and journals to get it as close to the truth as I could. I was so immersed in 19th-century speech I began to speak the same way. At one point, I told someone I was 'sensible' of their ideas."

Thompson, said his children who are aged nine and 11, are "something to fight for." Nevertheless it is a painful existence.

"I feel like a 100-year-old man. There are times when it feels like you have run a marathon and then someone puts you on top of a 20,000ft mountain. I'm just gasping for breath.

"While I was writing the sitcom a plastic tube slipped out of my back. It was draining the pus out of my lung and then about two feet of stinking tube slithered out. The smell was disgusting.

"It's a nasty disease really, cancer."