NICK BAKER has no great ambition to sail across the Atlantic, let alone single handedly, and it is not a prospect he relishes. Plain scary, is how he describes it. So why is he doing it? The short answer is for charity, to give something back to a world in which, until recently, he has had a pretty fortunate ride. The longer answer is more complicated and one that he can barely articulate.

In June 2001 Nick, then 42, discovered that he had lung cancer. No, he isn’t a smoker and neither is anyone in his family, though he admits he worked too hard and was averagely unfit — he got his exercise running for the last train from Waterloo to Hampshire. But he felt and looked well, and he still does — he is one of those people who radiates vigour. So the diagnosis, which followed a casual remark to his GP about a rattly cough, was surprising.

Within a week surgeons had removed a third of his right lung and as he lay in hospital he wondered how he might react positively to his situation. “It’s the corny thing, this is your chance to put something back,” he explains. The idea passed and as he returned to his life as a yacht broker, husband and father, daily concerns took over again.

Then, in April 2003, tests revealed that the cancer had returned to his left lung. Aware that 95 per cent of lung cancer patients die within five years of diagnosis, Nick remembered his good intention and decided that this time he must follow it up. So on Friday he left the Canaries in a 50ft (15m) boat called Aqualung with the intention of sailing to Antigua, and the aim of raising as much money as possible for four charities — the Institute of Cancer Research, the Winchester Medical Foundation’s Magpie Cancer Centre Campaign, Merlin and Encompass.

To this end, his City contacts have been good to him: the finance for the boat has been provided by the bankers Ansbacher, and Pantaenius Insurance has covered him even though he is, in their words, “a crap risk”.

Nick is a tall, skinny man who fizzes with enthusiasm. He is also a product of Eton and Oxford, and not given to negativity or emotional outpourings. He smiles a lot too, but if I am any judge, he is also a realist. So Nick, is this response to the cruel circumstances in which you find yourself merely a positive way of using them, or is it a way to distract yourself, perhaps an act of defiance?

“It’s definitely a way of turning a negative thing to some good,” he says. “Yacht broker with lung cancer sails the Atlantic sounds dramatic and I hope I can raise a lot of money. So I’m afraid I’m using it. Psychology behind that? Wouldn’t want to look at it too closely. Yes, it’s defiance to a certain extent. I’ve always had a charitable urge and it’s easy to write the cheque and think you’ve done something. Buying and selling expensive yachts doesn’t help people in difficulty. It’s no good me flying to Africa to help starving babies because I’m not qualified and I’m a bit squeamish. But I can help to raise some money so that someone else can do it.”

By doing something risky? Nick has sailed since he was 14, though he describes himself as no expert. But with his characteristic good cheer (not to say understatement) he insists that what he is doing is no big deal.

“Statistically the chance of a gale where I’m going across is 5 per cent,” he says. “I’m living on a 5/95 spread already, it’s just another one. Some insurers did ask, is he likely to commit suicide in the Atlantic? Absolutely not. If something goes wrong it’s an accident. Very straightforward. I’m really, really, really not ready to die. Which is fair enough for a man of 46. And some days, I understand, it can be incredibly pleasant: sunny, music on, something nice on the cooker, tranquil, a book.

“There is a danger one would be introspective, maybe on the sixth, seventh, eighth day when you’re still not half way. I think that would be very dangerous. I do recognise that lung cancer may kill me, I don’t recognise that it will kill me. That’s the denial, isn’t it?

“I do not believe I’m in denial, but that’s what denial is. If not letting it rule my life is denial — I don’t know, I’m not sure that denial is actually bad. I think you can accept certain realities but you don’t need to force them on yourself. I don’t wake up every morning and say, ‘Oh my God, I’m dying of lung cancer’. I view myself as living with lung cancer, which is a different thing altogether. I emotionally acknowledge that statistically it is very likely to kill me, and there are days when I think this is a bit of a bugger, frankly, but you can’t stop it. I can’t sit at home being miserable, so I don’t. You have to try to cope with it as best you can by being positive.”

Nick’s cancer is not being treated as it does not respond to chemotherapy or radiotherapy, and there are no proven drugs available. He has found the last few weeks stressful: finding sponsorship, getting the boat to the Canaries, ensuring it is in good condition, and trying to find time for his family — his children are 16, 14 and 11. “I’m not a brilliant father, certainly, but I’m certainly not so immersed in my work that I don’t know my children. I love being with them,” he says.

“I’m very much looking forward to it being over and coming back to Hampshire and living tranquilly, resuming whatever is a normal life.”

• To donate to Nick Baker’s nominated charities, go to www.aqualungtrust.org, or send a cheque to The Aqualung Trust, c/o Clyde and Co, 51 Eastcheap, London EC3M 1JP