A young man called Bill stands in the shadows behind a curtain at a converted paintworks factory in Bristol, now a TV studio. "To be honest," Bill says, "I'm a bit shell-shocked."

"This is it!" yells a man called Jim. "Concentrate, Bill! Hit it! Hit it! Hit it! Let's do it, mate! Come on! Come on!"

"I'm bricking it," says Bill.

"Go out there!" Jim says. "Fierce! Do it! Be affirmative, man! Win some money! Do it! Positive! This is your moment! This is your chance! GO! GO! GO! GO!"

And, at that, Bill steps out from the shadows to rapturous applause, and he proceeds randomly to open the first of 22 boxes.

Nine months ago, I was on a treadmill at the gym. A Channel 4 afternoon gameshow called Deal Or No Deal was on the TV. I'd never seen it before, so it took me a minute or so to understand what was going on.

Twenty-two contestants stood behind 22 boxes. One of them, Fin, was selected to be that day's player. There was a cash prize inside each box, from 1p to £250,000. Each time a box was opened, the box, and whatever cash prize was in there, was out of play. Fin would win whatever money was left in the last box he opened. From time to time, a telephone rang and a mysterious person on the other end, The Banker, tried to tempt Fin to stop opening the boxes by offering him a cash settlement. And that was it. That was the game.

"It's all luck," I thought. "It's a gameshow with no skill. He's just opening boxes. What a terrible idea."

Forty-five minutes later, I was convinced Deal Or No Deal was the greatest game show I'd ever seen, full of unbearable drama and unexpected weirdness.

At first, Fin looked pretty ordinary. But then he produced a scrap of paper from his pocket and showed it to the presenter, Noel Edmonds. "It contains distilled wisdom from Paulo Coelho's The Alchemist," he said.

"I like the sound of this, Fin," Noel replied. "You've got a sensitive, almost spiritual side."

"How does Fin think distilled wisdom from Paulo Coelho's The Alchemist will help him choose the right boxes?" I thought, as I jogged. "It's all luck. And when did Noel Edmonds suddenly get so mystical?"

There was a close-up of the scrap of paper, upon which Fin had scribbled, "Listen to your heart."

Suddenly a trance-like state overwhelmed Fin as he scanned the boxes.

"What's going through your mind?" Noel asked.

"I'm trying to just let the numbers come to me," Fin said.

"For a big guy, you're looking incredibly serene," said Noel.

"I'm listening to my heart," Fin said. "Box number 16, please."

It was opened - £5. The audience cheered. Now Fin wouldn't go home with the paltry sum of £5. And so it continued. Fin's psychic trance state turned out to be an astonishing triumph. He opened the £1 box, the 50p box and the 10p box. Noel and the audience and I watched awed, as if witnessing a miracle.

"The way you're playing the game is actually more powerful than luck itself!" Noel said.

It was turning into one of the most exciting television-viewing experiences I'd ever had. Each time a box was opened, the tension was so agonising, I was practically running a four-minute mile. Although this was quarter past four in the afternoon, four million viewers - nearly half of everyone watching TV at that moment - were watching Fin.

Then The Banker phoned and offered Fin a huge cash settlement of £44,000. The audience gasped. A mystical look crossed Fin's face.

"No deal!" he said. There was cheering. And then disaster struck. Fin opened the £100,000 box, followed, devastatingly, by the £250,000 box. He ended up walking away with a relatively crappy £10,000.

Everybody in the audience - including Noel - went quiet and looked embarrassed and even a little ashamed. The mood was what I imagined it must feel like when somebody turns on all the lights at an orgy. The fact is, Fin should have accepted the £44,000. Listening to his heart and making decisions based on psychic impulses cost him £34,000. It was a victory for rational and vaguely negative thinking.

"My God," I thought, as I climbed off the treadmill, exhausted. "They're in a bubble. They've got no sense of reality. They have, in Noel Edmonds, a charismatic leader who believes in nutty things. It's like a religious cult! An incredibly nail-biting and entertaining cult, brilliantly presented by Noel, but a cult none the less."

And so I phoned Endemol, the show's producers. I asked if I could be a fly on their wall. The programme is filmed in Bristol, they said. The first anniversary show would be filmed in early October. I was welcome to come along.

It is early October, in Bristol, and despite all the backstage motivational pumping by Jim the contestant carer, Bill is having a terrible game. He's randomly opening all the wrong boxes. They film three shows a day, and this is the last. It is especially awful to watch Bill in such straits because this morning another contestant, Dan, won £70,000.

I'm sitting in the green room next to Pete the coach driver. Pete ferries the contestants between the hotel and the studio. His contact with them is minimal. This morning he announced to the coach that he would be grateful if people stopped calling him Driver.

"I hate that," Pete said. "My name is Pete."

Now, as we watch Bill's painful show unfold on the monitor screen, I can hear Pete whisper to himself. I listen closer. He's murmuring, "Come on, Bill. Believe. Keep the dream alive."

But it doesn't work out. Bill opens the wrong boxes to the end and walks away with a devastatingly small £750. He emerges from the studio drained of colour. We climb on to the coach. Pete drives us back to the hotel in silence.

Deal Or No Deal was invented within Endemol's Dutch HQ. It has sold to 45 countries, from Albania to Vietnam. When Endemol developed the format for British television, they came up with a brilliant idea. In other countries, such as the US, the people behind the boxes, the box-openers, are professional models, former Playboy centrefolds, etc. They all wear identical showgirl costumes. UK Endemol's brilliant idea was to make the box-openers fellow contestants - players-to-be. This means they're all sequestered away together at a hotel in Bristol, sometimes for weeks on end, away from the anchor of their homes, while they await their chance to get out from behind the boxes and become the main player. Consequently, an intense group bond forms. Late at night in the hotel, tiny things become huge things. Emotions are heightened. And in the morning, when filming begins, you can feel the drama in the winces and the cheers and the looks of love and hate that pass between the contestants.

According to the Cult Information Centre's pamphlet Cults: A Practical Guide, cult leaders routinely employ 26 skilful techniques to keep their followers under their spell. One of the main ones is "Isolation: inducing loss of reality by physical separation from family, friends, society and rational references."

Endemol, which also makes Big Brother, realises that isolation doesn't only produce good cults, it also produces good television.

Now, as the coach trundles miserably back to the hotel, I realise this is the first time that the mood has been at anything less than a fever pitch of positivity. Jim the contestant carer is forever giving motivational talks. We're getting about four every day.

"GROUP CHEER!" Jim constantly yells, his eyes aflame.

I wonder if this is in any way because of Noel Edmonds' famous antipathy towards negativity. Noel writes in his recently published self-help book, Positively Happy, that he can't abide negativity in the workplace. Noel hates negativity. He even advises readers, on page 88, to dump their sexual partners if they are too negative. I can't help thinking that, if I were Noel Edmonds' lover, he would dump me.

"But surely a bit of negativity makes you - you know - interestingly spiky and sassy," I suggested to Noel earlier, during a break from filming.

"I simply will not get involved with people who are negative," Noel replied. "I won't tolerate people in the workplace who are negative. I like realistic people, but negative people? No. Just get rid of them."

"I have a habit of being a bit negative sometimes," I said. "I'd hate my wife to read Positively Happy and dump me as a result."

"Then be careful," Noel said, looking me in the eye, "because she might."

There was a silence.

Actually, Kevin the studio warm-up man was a bit negative yesterday. His job was to buoy up the audience into a frenzy of excitement, and he did have an upbeat voice, but the things he said were terribly miserable. "I'm so sad," he told the audience, "that if I went to a wife-swapping party where everyone throws their keys into the middle, I'd be the only one to walk home alone! That's how ugly I am!"

The audience shuffled uncomfortably in their seats. That was yesterday. Today, Kevin's nowhere to be seen. He's been replaced by a far more cheerful and upbeat warm-up man called Mark.

It is 10pm, back in the hotel. I have a drink with contestant Tony from the West Midlands. Earlier, during recording, Tony was standing behind Box 8 and Noel mentioned that he thought he looked like a funeral director. It got a laugh: Tony does look slightly undertakerish, with white hair, a white moustache and a long, thin face. Now, unbeknown to everyone else, Tony is desperately worried about it.

"I'm semi-retired," he says. "Everything in my life revolves around quarter past four. I do the washing, the cleaning and then I sit down. Deal Or No Deal is an addiction for me. So actually to get through the auditions and on to the show... I'm dreaming! Apparently the chances of becoming a contestant are 70,000 to one. And I make it through all that, and Noel calls me a funeral director." Tony pauses. "If only he could see the real me. Maybe I should have laughed or something. But to stand there and laugh at nothing? It's hard. And I didn't sleep well last night. There were police cars going up and down all night. Was Noel aware of that?"

Suddenly, Tony stops and glances at my notepad. "Where's this information going?" he asks. "Is it going to The Banker?"

There's a lot of paranoia among the contestants that things they say and do in the hotel might be relayed to The Banker - the mysterious figure on the other end of the phone who is never seen or heard. They fear that when it's their turn to play, The Banker might give them low cash offers if they've been deemed to have behaved in a desperate or cowardly or negative way back at the hotel.

"It isn't going to The Banker," I say.

Tony pauses. He narrows his eyes. "Are you giving it to someone who'll give it to The Banker?" he asks.

"No," I say.

At this, Tony relaxes. And it's true: Noel hasn't seen the real him. He's a warm, lovely man. As we drink, he keeps asking me, "What can I do to make Noel realise that I'm nothing like a funeral director?"

Every night after dinner there's a contestants' meeting. It is a chance for the three main players of the day to dissect their games. Bill - the £750-winner - takes the floor.

"I just want to say," he says, "that The Banker was a twat and a dickhead, and thank God he wasn't standing in front of me." Bill sits down again.

"You stood strong, Bill," says a contestant called Edward. "That's what matters. You stood strong."

I glance over at Dan, today's £70,000 winner, who, ironically, is probably the least mystical person here. He's always laughing to me about his fellow contestants' crazy systems. And then he went and won £70,000. There's a big smile on Dan's face now. His beautiful girlfriend is draped over him. They spent the afternoon shopping for designer clothes. I glance back at Bill, looking hunched and lonely. I resist the temptation to think that this was somehow predestined, that Dan looks a winner, and always did, and Bill looks a loser. But I don't think that, because it is an irrational thing to think.

Then I am asked to take the floor to introduce myself. "Some people apparently believe that I'm not really from the Guardian," I say, "and am, in fact, The Banker's spy. Well, I just want to say, I might be!"

I pause to receive laughter, but there isn't any.

"We're serious," a few people say. "Are you or aren't you working for The Banker?"

"I'm not," I say.

They give me three cheers.

Some contestants get drunk. The drinkers are, I've noticed, the ones who realise, like I do, that the box opening is all about luck and not at all spiritual. Maybe the weight of that knowledge is enough to drive you to the bottle. Other contestants sit quietly and concentrate on their systems.

Ned from Liverpool has a system. He shows it to me. It is a series of boxes and Xs, like some weird periodic table, printed on a neatly folded piece of A4.

"What I did," Ned says, "was discard the 17 numbers that make up my name: NEIL THOMAS CULSHAW. For instance, the number 1 has gone because it corresponds with the letter A. I'm left with five numbers, and I've put them in the order of which boxes contained the highest amounts during last week's shows. But I've reversed the order, based on the assumption that if they contained the highest amounts last week, they'll contain the lowest amounts for me. So, bearing all that in mind, the five numbers I'm leaving to the end are 16, 17, 10, 22 and 18."

"So you believe you've calculated that when you're the main player, box 18 will be the box most likely to contain £250,000?" I ask.

"Yes," Ned says confidently.

"Complex," I say.

"Not really," Ned says.

I'm surprised that so many contestants still put such stock in their systems. If the show has taught us anything over the past 12 months, it has taught us that systems don't work and that people aren't telepathic. Contestant Steve has a lucky number, but he won't tell me what it is, in case sharing the information inadvertently robs the number of its power.

Last week, John - who claimed to be both telepathic and have a foolproof system - had his chance as the main player. John, a retired bank manager, had assiduously analysed 105 shows. At night in the hotel, he sat apart from the others, studying spreadsheets. He concluded that boxes 1, 2, 5, 6, 18 and 19 were the luckiest. John's telepathy manifested itself in a tingle in his fingers. If he laid his fingers on a box, and his fingers tingled, he knew the box contained a high amount. John was convinced his telepathy, coupled with his system, would make him unbeatable.

In the end, John walked away with £1.

None the less, the contestants tonight are undaunted. "John wasn't telepathic," says Nalini, "but I've always been telepathic. One night I jumped out of bed. I said to my husband, 'Something bad has happened.' He said, 'Don't be ridiculous.' I said, 'I mean it. I can't go to work because I know something terrible has happened.' And later I discovered that this was the exact moment that my eldest son died. It was in the Maldives. That's the other side of the world. The exact moment. That was 10 years ago."

Still, Nalini says she doesn't want her turn as the main player to come just yet because that means she'd have to leave the bubble and go home.

"I love being here," she says. "My husband is a driver for Iceland, and on Saturdays he drinks." She shrugs. "So I prefer being here in the hotel. This is a holiday." Then Nalini pauses and moves closer to me. "Some people think too much," she says. "They go mad in the hotel."

But for Bill, who just walked away with a terrible £750, there is no talk of systems or psychic powers any more. For him, the bubble has burst.

"I'm not worried any more that I lost," he tells me. "I'm worried about coming over as a twat on TV."

"You didn't," I say.

"If people say, 'There's that twat', it'll make the rest of my life very hard," Bill says.

I go to bed.

In the middle of the night, the fire alarm goes off twice. I have to traipse down nine flights of stairs to the car park.

The next morning, everyone is exhausted. I visit Noel in his Winnebago. It is parked deep within the Endemol complex, near a dried-up river. Inside, it is very luxurious, all cream leather seats. Les Dennis's far smaller and less deluxe Winnebago is parked next to it. Les Dennis is filming a Channel 5 game show called Speculation in another studio.

"Les Dennis can have the big Winnebago when he gets the ratings we get," Noel says.

I glance stealthily around the Winnebago for little clues that might reveal dark secrets of Noel's personal life. Noel's love life has been of interest ever since he made it known earlier this year that he asked the cosmos to provide him with a woman.

Noel believes that if you order wishes from the cosmos, the cosmos will oblige, as long as you follow the correct ordering protocols: you must write down your wish on a piece of paper. You absolutely have to be positive. The cosmos will not accept negative wishes. You must keep your wish general. The cosmos won't, for some reason, grant overspecific wishes.

As Noel explains to me the ins and outs of cosmic ordering, I involuntarily look dubious. Immediately, Noel changes tack to insist he hasn't gone "off with the fairies".

"Yes, the word cosmos might sound off-putting," he says, "but you don't have to call it cosmos. Cosmos is just a word. You can call it anything you like. You can call it Argos, or MFI."

It strikes me that Noel Edmonds is probably the only modern-day spiritual guru who would even consider Argos or MFI as alternative names for the cosmos. That's the odd thing about hanging around here - the mystical people are not at all new-agey. They are retired bank managers. They work in betting shops. They are Noel Edmonds. The last time I saw Noel was 10 years ago. He barged past me in some country house hotel, heading for his helicopter - the epitome of the no-nonsense Conservative businessman and celebrity, off to do some deal. He was nothing like the vulnerable, spiritual Noel sitting in front of me now. If anyone doubts the extent to which mysticism has permeated the hitherto secular corners of British society, they should spend a couple of days behind the scenes at Deal Or No Deal.

"I wrote to the cosmos that I would like to meet a woman who'll make me laugh and make me happy," Noel tells me. "I wrote that I'd like a relationship that's not too heavy, with an attractive lady, and I'd like her to walk into my life by the end of September 2005. And she did!"

There is a short silence.

"She wasn't the person who sold her story to the Sunday People back in July, was she?" I ask.

There's another silence.

"Yes," says Noel.

Marjan Simmons, The Sunday People, August 2006: "He was a very tender and lovely kisser. When I woke up with him the following morning, I felt completely at ease and his first words were, 'Cup of tea, darling?' He was a very giving man in all aspects and satisfied me in every way. Noel had his own special song for us. It was You're Beautiful by James Blunt. But once he was back at the top he didn't need me any more. I felt he just discarded me. He was a hypocrite who used me to make himself feel more positive about himself."

"So that turned out to be not so good," I say. "Maybe if you'd written down, 'I want to meet somebody by the end of September and I don't want her selling her story to the Sunday People...'"

"No, you can't do that," Noel interrupts, "because that is a negative. The cosmos will accept only positive orders. The word I probably missed out was 'trustworthy'."

I continue to peer surreptitiously around to see if I can spot anything weird or secret in the Winnebago. Noel almost immediately notices what I'm doing. "Go and have a look in the bedroom," he says. "Go on."

I look doubtfully at him. "Are you sure?" I ask.

"Have a look in the bedroom," he repeats.

I shoot Noel a slightly suspicious glance and then I wander into his bedroom. I have a good poke around. And, unfortunately, I find nothing incriminating. Still, it was nice of him to offer.

I tell Noel that I can't understand why he doesn't give up the mysticism. I've spent three days here, watching three shows a day, and I've seen so many disappointments, so many broken dreams, so many systems - telepathic or otherwise - that didn't pan out. And Noel has presented 300 shows. By now he must know that life is just random.

Well, first, Noel replies, it was the cosmos that gave him Deal Or No Deal. In 1999 the BBC had unceremoniously dumped him, after 20 years as a star presenter. It looked as if he'd never be on TV again. He was a workaholic without work. So he spent five fallow years throwing himself into various businesses and charities - the British Horse Society, some anti-wind farm lobby group called the Renewable Energy Foundation, and so on. But he asked the cosmos for a new work challenge, and the cosmos gave him Deal Or No Deal. It was a huge and instant success, nominated for a Bafta and winning a Royal Television Society award and a Rose D'Or, all within a few months.

"Have you looked up Deal Or No Deal on the internet?" Noel asks. "It can do your head in. Did you know that someone's compiling a dictionary of my phrases?"

This is true. A large Wikipedia entry is dedicated to Noel's oft-repeated expressions ("Some people call it an entertainment drama, some the Red Box Club... Welcome to Planet Tension!" "It's not how you start, it's how you finish." And so on).

"Somebody else," Noel says, "is tracking the repetition of my shoes, trousers and shirts." Noel is thrilled. "I'm delighted people are reading so much into it. I want to be popular. I want people to like me. Not long ago I talked to someone in the audience and she went to pieces. Just because I was talking to her! It is really important I keep my feet on the ground here."

I don't think Noel should be thanking the cosmos for the success of Deal Or No Deal. I think it takes a rare presenting talent to make the opening of 22 boxes so gripping.

But then Noel says there's something else. There's another reason why he still believes. He says that after 300 shows he now knows - practically every time - how someone's going to do before they've opened a single box.

There's a silence.

"How?" I ask.

Noel pauses. "How deep can I go here?" he says.

Then he says, "Take Edward. Edward, I'm really not sure about. I've got a funny feeling it may go horribly wrong for Edward."

Noel says he knows this just by the way Edward walks, by his aura. You can tell winners by the way they walk, and Edward doesn't walk this way. Yesterday, another contestant, Mark, told me that Edward needed a big win more than anyone here: "Edward's got nothing," Mark said. "Literally nothing. He's completely skint."

I know something Edward doesn't know. I've seen the call sheet. Edward's game is going to start in a couple of hours.

Just before I leave Noel's Winnebago, I spot a typed sheet of paper lying on the kitchenette. I look closer. It contains notes about what the contestants got up to in the hotel last night.

"It started because of ill health," Noel says. "Everyone was getting colds. I needed to know what was happening."

But once the colds cleared up, the daily reports to Noel continued. For example, Noel says, if a pair of amorous contestants are seen leaving the bar together, a production assistant will write down the news and Noel will read about it at breakfast. He probably won't refer to it during the show, he says, but it is important for him to know what's going on. Today's sheet reads, "Tony is very sensitive about your funeral director comment."

I leave Noel and wander back to the contestants. They're in make-up. Jim is giving them a motivational talk.

"The sun's out!" he says. "It's a brand new day! Let's really lift ourselves! Are we going to stick it right down The Banker's throat? Yeah? Yeah! Momentum! Get momentum! GROUP CHEER!"

Everyone cheers.

Tony is still worried about Noel's funeral director aside. He says he telephoned his wife last night in a terrible flap. "I said to her, 'Rita? Am I miserable?' She said, 'You're not.' I said, 'I love you for ever.'" Tony pauses. "But, Jon, you know what? I have a plan."

He hands me an envelope. I open it to find a photo of Tony's father standing next to Lester Piggott.

"Noel is president of the British Horse Society," Tony says. "If I can get him to see this photo... Noel will know that a horse lover can't be miserable."

Inside the make-up room, a contestant called Madeline is talking about last night's fire alarms.

"I had to walk down 10 flights of stairs in my nightie," she tells the make-up lady. Then she spots Jim the contestant carer. "But you have to laugh, though, because it was really funny," she adds quickly.

We walk into the studio. It is time for the contestants to choose their box numbers. This is done randomly: they reach in and grab ping pong balls from a bag.

Contestant Nalini, who claims to be telepathic, turns to contestant David and says, "You're going to pick number 7."

David reaches into the bag and pulls out ping pong ball number 7.

Nalini smiles to herself. Everyone goes quiet.

Noel emerges from the wings and wanders up the line, saying hello to the contestants. He reaches Tony.

"How are you?" he says.

"HA! HA! HA! HA! HA!" says Tony, throwing his head back and letting out a huge, Santa Claus-type laugh. Then Tony spots me. He winks, as if to say, "I did it!"

I give him a surreptitious thumbs-up.

And then the recording begins, and - as I knew he would be - Edward is picked. This is Edward who is penniless, Edward who needs it more than anyone, Edward who, Noel has psychically predicted, will have a terrible game because he doesn't have the aura of a winner.

Two hours later, and the contestants are crying. Nalini blames it on the fire alarms. "We're all so tired," she says. "If we haven't got the energy, how can we give off positive vibes? That's why Edward opened all the wrong boxes."

Whatever; Noel was right. Edward walks away with just £1.

· The first anniversary spectacular of Deal Or No Deal will be broadcast on Channel 4 on October 29 at 5.55pm. Some players' names have been changed so we don't reveal the endings of programmes that haven't yet been broadcast.