When David Blaine was first planning his London trip, he had in mind an underwater stunt. The idea was to jump off Tower Bridge into the River Thames in chains, wriggle free and emerge triumphantly from the murky deep. For months he practised holding his breath under-water. “I can do four minutes,” he tells me proudly.

But acts change, plans evolve and there is a lot more mileage in a performance that lasts 44 days and 44 nights than four minutes. There are the live television and documentary rights for a start: the first act would have amounted to little more than a newsflash.

The new stunt offers fewer thrills and spills, but is ultimately more riveting. We are going to watch Blaine slowly starve, suspended near Tower Bridge in a see-through, Plexiglas box, 7ft long by 7ft tall by 3ft wide, for six agonising weeks.

The drama will unfold on September 5 by the river instead of in it. He will urinate through a catheter covered by his trouser leg and will carry a discreet backpack with nappies.

He will be given water by tube, but not food, which should limit “number twos”. It is, he claims, the most “extreme exercise” he has attempted. “Everything I’ve done before is irrelevant. This one is going to be different.”

It is said with the exaggeration of the showman, for of course there are plenty of similarities with his previous stunts, each of which demanded an iron discipline, fasting ability and — always fascinating to punters — bowel control.

Blaine, 30, became famous for encasing himself in a block of ice for three days, emerging visibly disoriented and unable to walk. He has also buried himself alive in a glass coffin for seven days and last year stood on top of a narrow 83ft pillar in New York for 35 hours before plunging into a pile of cardboard boxes.

As with his iceman act, he was carted off in an ambulance: a nice touch but also a necessary one, which we will probably see again at the end of his new stunt.

Blaine is both magician and mystic; showman and shaman. When I meet him in his New York bachelor pad, I’m not sure whether he is a trickster or the real McCoy. Will my eyes deceive me?

I am greeted by two blondes at the door, who tell me they have just witnessed a ghastly sight: Blaine has been sticking an acupuncture needle through the back of his hand and out of his palm. “Yuk, you should have seen it,” they giggle. “We had to dive under the covers.”

They are sisters, they tell me, and my eyebrows shoot up. Has Blaine been entertaining them both in bed?

I should have known that, with Blaine, nothing is as it seems. The party girls turn out to be old friends of his. One is happily married, lives in London and knows the News Review section of this paper intimately. She can’t be much of a groupie, I conclude.

The other soon goes off to meet her boyfriend, leaving Blaine to show me his acupuncture trick.

I can vouch for the fact that the skin of his palm stretches revoltingly as the point of the needle goes through. Yet I can’t help feeling wary, for Blaine the illusionist makes his living challenging the evidence of our own eyes.

He is an expert at card tricks and can levitate in thin air. Although fellow magicians have sometimes scorned that he’s an amateur at it, he’ll be bringing his “street magic” as well as “endurance art” to London for a television special.

Blaine doesn’t mind admitting some of his acts are fake: not long ago he shocked a television audience by pulling his beating heart out of his chest. It was a £19,000 state-of-the-art replica, he freely confesses.

He does appear, however, to have a masochistic liking for pain, which makes me believe the needle really did pass through his hand. Suffering fascinates Blaine, although he insists his stunts are about controlling his body, rather than hurting it.

Why should we want to watch you torture yourself, I ask? “Seeing a man endure and overcome his fear shows we’re all capable of enduring more than we do,” he replies solemnly. Blaine’s small talk, I find, is pretty heavy.

You must have a death wish, I say, but he shakes his head. He loves the “heightened sense of awareness” that such challenges bring. “You’re living truthfully in the moment. That’s when you’re at your clearest.”

Oddly enough, Blaine makes no distinction between petty magician’s tricks and his remarkable feats of endurance. “They all spark wonder and intrigue. They make people leave their shell for a minute. They’re not thinking about their bills or their problems,” he says.

During his stunts Blaine has the ability of a mystic to control his thoughts. “Anybody can stand torture and they do. You have to. Where are you going to go?” he points out reasonably. Whenever he falters, he thinks of Primo Levi, the chronicler of Auschwitz, who had no choice but to withstand horror. In tribute, Blaine has tattooed Levi’s concentration camp number on his arm.

Of course, Levi did not have the luxury of devising his own torment, which makes Blaine’s hero worship misguided.

As we head for breakfast at a macrobiotic cafe, where — to my taste — the food is barely edible, I begin to understand Blaine’s compulsion for self-harm. Even as a boy he pushed himself to the limit.

His mother was his rock: mother and father rolled into one. He never knew much about his father, although he has a hazy memory of seeing him as a toddler. It was his mother who bought him his first set of tarot cards at the age of five and encouraged him to spend hours at the library.

He read books about magic and science and practised tricks for hours on end. He was weird, there was no doubt about it. “At the swimming pool, I’d get adults to bet on how many laps I could do underwater and I’d win, even if I came up purple.”

When he was 19, his mother was diagnosed with cancer. Blaine waited on tables at another macrobiotic restaurant, convinced that a strict diet would cure her. He had hoped to learn how to cook macrobiotic food.

There was no time to save her, but Blaine still thinks she might be alive today had she followed the diet to the letter. “I wasn’t prepared for her death in any way,” he admits.

“I escaped the pain rather than dealt with it. When you bury pain it becomes a pit in your stomach and eats you from the inside out.”

After that, “I became a man with a mission. I felt I was abandoned by the world and had nothing except my magic.”

Blaine hung around clubs and agent’s offices, accosting celebrities such as Jack Nicholson, Madonna and Robert De Niro, who were impressed by his impromptu sleights of hand. A buzz spread until he had his own agent.

As his fame grew, Blaine partied with stars such as Leonardo DiCaprio and leggy supermodels. Spike Lee filmed adverts for him; De Niro bought the rights to his life story and the comparisons with Houdini rolled in.

Yet the drive to succeed, Blaine insists, is “the opposite of what brings happiness”. The more successful he was, the darker his moods became. For a start, none of the girls he dated was a patch on his mother.

“I was always comparing them to her, which was a no-win situation for them.”

The fast life also interfered with his disciplined schedule. “If you’re out at a night club, you’re not achieving much. Every day I’m not working on new magic is a wasted day,” he says.

Not surprisingly some old pals have peeled away. “We’re all right, but we’ve moved on,” he says of DiCaprio.

Blaine is now friends with people who are as unusual as he is such as Uri Geller, the paranormal showman who inspired him as a boy, and the actor Christopher Reeve, who endures his paralysis with more fortitude than Blaine has ever had to muster.

Although no recluse Blaine is developing a pronounced ascetic streak. Watching him press that needle through his hand, I am reminded of the saints’ mortification of the flesh. The pillar stunt was explicitly modelled on the hermit Saint Simeon Stylites.

I had taken the 44 days to be some sort of biblical allusion, but in fact it relates to his birthday on April 4 (the fourth month).

Just as Saint Simeon built an ever taller pillar to keep crowds of worshippers at bay, so Blaine has to keep outdoing his acts. It is a pressure that never wears off.

He keeps his ideas in a file which he constantly updates. One potential stunt, he tells me, involves a high rise rope trick; another has to do with mirrors (he never gives more than the basics away).

He then takes me to a meeting with an avant-garde gallery owner in Manhattan who is proposing to exhibit Blaine as a performance artist — of what kind is yet to be decided. I can see he is attracted to the idea that he is a work of art.

“My work is going to get much better,” he tells me intently. “I think I’ve only put in 10% of what I can achieve.”

By the end of the interview, he has almost persuaded me that he is more than a magician. Perhaps he really is an artist, I begin to think.

As I put on my jacket Blaine asks me where I have put his golden ball. I have been fiddling with a small, tasteless globe, inscribed with favourite words of his such as “endure” and “inspire”.

For a second, I fall for the trick and start searching the sofa for it. But, of course, I find it hidden in my pocket. How corny is that? Forget the stuff about sainthood. He’s a performer. What did I expect? Walking on water?

Let’s see what happens at Tower Bridge.