I have a guilty secret. It is a very British guilty secret. In France I would need neither to be guilty nor shy about it. There, my secret is practically a national pastime. In this country it is a different matter entirely. In this country admitting that you are - and here's the guilty secret - totally, carnally fascinated by extraordinarily expensive food experiences, puts you in the same category as foot fetishists and crack heads; a deviant, out of step with society, in thrall to truly unnatural appetites.

I should explain what I mean by 'extraordinarily expensive'. I'm not talking about £70 a head dinners in London restaurants. Obviously £70 is a lot of money, but this context £70 is also nothing: take off the cost of wine,the VAT and the service, divide it by three for each course and that amounts to no more than £25 a dish. That does nothing for me; it is Vauxhall Conference stuff, compared to the Premier League that I am talking about.

Whatever you might have read or heard it is actually quite tough to spend humungous sums of cash on food in Britain's restaurants. The tasting menu at Restaurant Gordon Ramsay, London's one restaurant with three Michelin stars, is only £85 and I use the word 'only' very consciously here. Sure, you can go à la carte at the Waterside Inn in Bray, where the most expensive single dish - sea bass studded with truffles - costs £45. But really: loose change.

To be fair London does now have a competitor of sorts, a new and hyper-expensive restaurant project by Mourad Mazouz, owner of the hip North African restaurant Momo, and Pierre Gagnaire, the revered Parisian three-star chef. They have taken over a grand building off London's Regent Street.

Naturally I have been fascinated with this enterprise from the moment rumours about it began circulating. As is always the case when I see a large price tag I want to know what level of eroticised delirium, what form of tumescent deliciousness, big bucks would get you. Early on I made an appointment to meet Mazouz amid the sawdust and the paint cans of his new baby, which is called Sketch. It is an amazing place. The walls of the gastronomic restaurant - called the Lecture Room - are padded in white leather with details picked out in gold leaf. There is a huge art gallery which, at night, turns into a brasserie.

Mazouz and I talked just a few days before opening night in the empty kitchens that will service the Lecture Room. I asked him how much dinner would cost.

'It depends on the cost of the produce,' he said. 'The number of chefs we have. The involvement of Pierre Gagnaire.' Yes, obviously, but how much? 'To tell you the truth, we don't know yet. We haven't written the first menu.' Make a guess, then. A stab. You must have some idea. Mazouz shrugs. 'Just for food it will be £100 a head.'

He was being coy. The Lecture room is now up and running. Starters cost around £50. There are main courses at £75. Think £150 per head for the food. £150? Is that all? I have to tell you I was hoping for so very much more from Sketch. I am terribly disappointed.

Here's what I mean by expensive: not long ago, for this magazine, I went to Alsace to write about the Auberge de L'Ill. It is one of the great institutions of French gastronomy, a restaurant which has held three Michelin stars since 1967, where the chefs have come from one family - the Haeberlins - for generation after generation. As I had flown out to meet them they invited me to be their guest for dinner and I found it in myself to accept. Had I been paying for it the dishes I was served - among them the seared foie gras, the lobster with ceps, the tripe salad, the salmon soufflé and the red mullet plus all the wines, vintage and non that kept them company - it would have cost 719 euros or £480, for one person. And more than two thirds of that cost would have been made up by just one dish and its accompanying wine.

The dish is a whole black truffle, wrapped in foie gras, encased in pastry, deep fried and served on a deep meaty reduction heavy with more black truffle. It costs euros129 or £82. To go with it the sommelier, a fine and generous man, served a 1994 Cos D'Estournel Saint Estephe, a huge, big-fisted Bordeaux. It appears on the wine list at euros330, or £211. The pairing cost almost £300 and it took me just 10 minutes to consume, even with the occasional break to look up and stare blissfully out of the window. That's £30 a minute, or 50p a second. And every second was sublime, a concentration of earthiness and intensity.

I am not, I hope, insensitive to other people's feelings. I fully recognised that a lot of people back home, among them my wife, might think what I was doing was obscene. I suspected that the fact I was not paying for it myself might just about redeem me in some people's eyes (the one occasion when freeloading could be seen as a moral positive). But the truth is I really didn't care either way. I was hooked on hyper-expensive food experiences. I wanted to find the people who would pay for these things themselves. I wanted to identify more dishes like the Auberge truffle. Along the way I found the £175 chicken, the £80 fillet of fish and the £50 pudding. Sadly I didn't get to eat any of them. But I did find someone who has.

We do not need fine art to live, whatever the pundits on Radio 4 may tell you. We do not need fast cars or jewellery or even fine wine. We do,however, need food. 'That's the problem with food,' says New Yorker Steven Shaw. 'It's so familiar because we eat it three times a day. As a result food is unfairly singled out for approbation when it comes to expense.' Shaw was once an attorney, but he became more interested in the lunches he bought his clients than their legal problems. Now he makes most of his living writing about restaurants. He is a prime mover in a website for foodies called egullet.com, where like-minded, consenting adults can discuss spending outrageous sums on eating out. He also has his own website called fat-guy.com.

There are, he says, two groups of people who are willing to spend large sums on food experiences. There are those for whom money is no object; for whom, however much it is, it's still not a lot.' And then you have people like me who devote a larger proportion of their available income than would be considered normal.' Steven reckons he spends around 100 per cent of his available income on eating out, which probably is more than normal. Does he feel the need to justify it? 'No. It's my money and I can spend it how I like.'

So what has he spent it on? 'The most expensive single meal was $760 for two at Alain Ducasse in New York, of which maybe only $100 was wine.' The rest - £440 - was spent on the white truffle tasting menu. And was it worth it? 'Absolutely. It was great.You know you're getting the best white truffles because Alain Ducasse is the guy. Personally I'd prefer to go there once and then eat rice and beans for the next month than deprive myself.'

The most expensive single dish he has ever eaten is the whole truffle en croute, served at Les Crayeres, the three-star restaurant of chef Gerard Boyer in Reims. 'I knew it would cost $150 and I was prepared for it.' It is, like the version of the dish at the Auberge de L'Ill, a whole golf ball-sized truffle wrapped in pastry. 'The moment you cut into it the steam rises and you get hit by the aroma. At first I was like,"oh my god, I've been let loose in the candy store" because I'm used only to having shavings of it. But you know what? The whole truffle takes away the mystique of it all.' So it was a disappointment? 'No I was glad I did it.'

What about the price? Can that be justified? After all a whole truffle may be expensive but it's not $150 expensive.'It's a rather primitive view of a restaurant to say that you are just going in there to buy food,' he says.'The only way you can rationalise it is to say that I'm buying an experience, not food. At the three-star level you can experience life in the way the richest person in the world experiences life.'

Steven is obviously a serious eater but frankly, compared to Jennifer, he is a rank amateur. Jennifer,who does not wish to be much further identified, is also a New York lawyer.She accepts that she is well off but not beyond the dreams of avarice. She is, though, wealthy enough to fly to France solely to eat, often by herself, making notes, taking photographs of dishes and saving menus. She visited her first threestar restaurant by herself in 1986 when she 17. It was Lucas Carton in Paris. Since then she has visited almost all the three stars in France, many of them numerous times and she often goes in pursuit of specific dishes. One of them was the fillet of bass with a layer of oscitera caviar at Restaurant Pic in Valance (a mere two star.)

'This dish is very interesting,' Jennifer says, 'Because it was created by the father of the current chef. It has a wine-based sauce the flavour of which changes as you eat.' It also comes in two different sizes: one has 15gms of caviar for euros89.The other has 25gms for euros119(£80). Which did she have? 'The bigger one. What's 119 versus 89? For the extra 10gms of caviar it seemed to be worth it. Too many people focus on the fact that because you eat it, there's no tangible asset at the end of the meal,' she says. 'I am a tourist of sensory experiences. I find food very sensual.'

The £80 fillet of fish may seem impressive but compared to what she did at Restaurant Bernard Loiseau, that was just a warm up. Loiseau serves a whole Bresse chicken, cooked in a sealed pot, alongside truffled rice. It can be served to four people or two and, either way costs euros259, or £166. Jennifer ordered it for one. Well, she was eating by herself and she did want to try it. What else is a girl to do? And it was great, yes? 'No, it wasn't terrific. It was not the best chicken dish I've ever had, but I wasn't disappointed.' And then she says, with impeccable logic: 'I don't resent the expense because how would I have known what it was like if I hadn't tried it?'

These hyper-expensive dishes are almost exclusively a feature of French restaurants. At Lucas Carton,for example, there is a dish of caviar, white onions and pistachios which costs £96 (£130 if you have it with the matching vintage champagne.) And at Marc Veyrat's restaurant, Auberge de l'Eridan, there is an assiette of chocolate that costs euros73. In this country there are - bar perhaps at Sketch - none of these destination dishes. As the great Albert Roux points out to me it is simply a matter of culture.'The average taxi driver in Paris will know the price of truffles,' Roux says, 'And if he can save the money to eat them he will.' There are probably few of London's black cabbies about which we could say the same.

Indeed in Britain if you really want to spend big on food, the only way you can do so is to pursue individual ingredients. Which brings us to Caviar House on London's Piccadilly, the site of the most expensive meal ever eaten in Britain. Most people think that took place at a restaurant called Pétrus, just around the corner from Caviar House, where a bunch of bankers spent £44,000 on one dinner. But all of that went on wine, says Natalie Rebeiz-Nielsen, managing director of Caviar House, who loves caviar so much she even has two pet sturgeon. The meal at Caviar House wasn't just about fat wallet bankers running their fingers down the wine list until they came to the largest numbers. 'It was two ladies who came in one afternoon. They ordered Almas caviar.'

Aah, Almas. Almas is the rarest form of caviar in the world. It comes from sturgeons that are between 60 and 80 years old, and is a pale amber colour. Natalie receives just four or five 1.8 kilo tins of Almas a year and she has sold her stock four years ahead. Each 1.8 kilo tin is worth £25,000.

I'll say that again: each 1.8kilo tin is worth £25,000. it is the most expensive food stuff in the world. 'The ladies ate £21,000 worth that afternoon.' Did you check their credit cards? 'No.I took it on trust.' We sit in silence, for a moment, thinking about that lunch bill. Eventually I ask her to describe the appeal of caviar. 'Theoretically you could live on just porridge and water,' Natalie says.'But caviar is about something else. It is about your taste buds. It gives you a little shiver at the back of your throat, the flavour of the whole ocean coming in.'

She asks me if I have eaten it. I admit, not often. She demands I come over to the front of the shop where a 1.8 kilo tin of black oscitera caviar, newly arrived from Iran, is being put into smaller tins for sale. She tells me to give her my hand, and make a loose fist, so that the base of my thumb forms a little platform upon which she can drop a large dollop of shiny caviar. 'I only ever like to eat it off my hand,' she says and I nod sagely. I take it in one mouthful, crushing the eggs against the roof of my mouth. It is sweet and slightly salty but not at all fishy. I decide I like caviar. Very much. As I am about to leave she says: 'Give me your mobile number. I'm going through my latest consignment over the next few days. It may contain a tin of Almas. If it does I'll call you and you can try that too.' I leave the shop in a daze.

I am very careful with my mobile for days after that. I make sure it is constantly charged and constantly on. I take to checking it works by ringing it from a nearby land line, just to see it buzz in to life. But, sadly, Natalie Rebeiz-Nielsen never does call me. Perhaps she didn't receive any Almas. Or maybe she decided I wasn't worthy of such a freebie. Or perhaps she simply forgot. No matter. Actually, I'm rather pleased. It means there's still another great foodie experience out there for me to try.All I need now is an awful lot of money.

· Are you a food fetishist?
Try our quick and easy quiz

1.Do you think Poularde de Bresse is:
a) A French porn star with very large silicon implants?
b) A kind of swimming stroke?
c) A breed of chicken that is easily worth 50 quid a pop?

2. You have £90 left in your bank account. Do you:
a) Spend it on new shoes for the kiddies?
b)Wager it on the 3.10 at Kempton?
c) Blow the lot on three servings of tagliatelli with white truffles at Locanda Locatelli.By yourself?

3. You are half way through lunch at Gerard Boyer's famed three star Les Crayeres restaurant in Reims,and about to taste his £100 truffle en croute for the first time, when the most gorgeous person you have ever set eyes on at the next table invites you to have raucous hot sex with them, but only if you leave with them Now! Do you:
a) Run out of the dining room with them so quickly you knock over your chair?
b) Ask them to join you at your table until you have finished?
c) Call over the Maitre d' and tell them to eject the weirdy stalker?

4. In return for five grams of Almas caviar would you be willing to:
a) Cross the road?
b) Cross town?
c) Sell your children into slavery and go on the game for the next 10 years?

5. Do you consider the Happy Eater All Day Breakfast to be:
a) A fine way to start the day as long as it is taken in moderation?
b) Just another dismal corporate marketing strategy but what can you expect from money men?
c) A crime against humanity for which the chief executive of the Happy Eater chain should be forced to eat his own feet?

6. £50 for the famed Marc Veyrat's dessert of an assiette of chocolate is:
a) An obscenity?
b) A joke,right?
c) A bargain?

score a) 1 b) 2 c) 5

Score
15 or above: You are a food fetishist of the first order and can invite us round for dinner any time.
6 - 14: You are Delia Smith.
6 or below: You are Chief Executive of the Happy Eater chain.

· Compiled by Jay Rayner