Adam, who is seven-and-a-bit, makes a list of his favourite foods. 'One: cheesy Quavers; two: cheesy pasta; three: Double Gloucester cheese, all melty, on white bread; Four: parmesan; Five: Wensleydale cheese; Six: cheddar.' So it's just cheese, basically, I ask? 'And toffee cake. And chips.' And what do you like least? 'Snails.' No, Ad, things that you've actually eaten? 'I really hate beefburgers. And Thai fish sauce.'

I'm pleased about the list. It's cheese-heavy, granted, but it has two brand-new items on it, the Wensleydale and the Double Gloucester. And Adam doesn't do new foods. The list is the direct result of an idea my wife came up with - an experiment. The terms were put carefully. Let's see if we can find some new foods that you'd like to try. We'll go to the supermarket and go up each aisle and you'll choose one thing, as expensive as you like, that you've never tried before but think you might enjoy. Adam nodded, a little dubious. Come on, we said, it'll be fun - it'll be a game. 'So I only have to taste the things - I don't have to eat them?' Yep, just taste them. 'What sort of things?' Fish, meat, vegetables, fruit, snacks, bread, puddings, juice. One of each. 'And cheese?' And cheese.

After school the next day he and I went down to Marks & Spencer - chosen because it has no brands. I didn't want Pringles or Heinz or pepperami sticks or any other TV-advertised label confusing the experiment. On the pavement, I handed Adam my wallet, which was part of the deal. He was still looking uncertain. What's the problem? I asked. 'I don't really like meat.' OK, we said you only have to try it. One taste. One bite. 'But,' he said, 'I'm afraid that if I don't like the food you'll shout at me.'

Being the child of a foodie must be hell. Like being the child of any sort of fanatic. For me, the fanatic, it hurts. Every dad looks at his newborn son and starts planning the adventures he'll go on with this new best mate - football, trainspotting, pot-holing. For me it was mushroom-hunting, winkle-picking, delicatessen-exploring. The thrills we'd have together on a motorbike-and-trattoria tour through Tuscany or fossicking through Borough Market. Hunter-gathering on the beaches of the Hebrides. How we would bond over food. But when Adam and I first sat down with a plate of boiled lobster that we'd caught and cooked together, he said 'Yuk!' without even trying it. I thought I might cry. If he'd come home with Black Sabbath tattoos, newly baptised into the Church of Beelzebub, it could hardly have been worse.

Adam, let it be said, has withstood the pressure quite brilliantly. After seven years of cajoling and pushing, deal-making, bribery and some shouting, he remains patient and understanding. He is sure of what he likes and pretty much unmoved by any parental insistence that he eat better and more widely. He believes that food is primarily fuel, and his tank is small. He knows what works - cheese, white bread, chips, pink sausages, plain rice, pasta with cheese, broccoli - and sees no reason to experiment. He's rational: 'I already have parmesan and cheddar, Dad - I don't need more cheeses.' 'But brown bread doesn't taste better - it's my mouth and it says white bread does.'

He knows also that he's a good kid - he sees worse all around him. If we go to Pizza Express he'll do his best - he'll eat garlic bread, or 'no sauce, no meat, only cheese pizza'. We've sat in many restaurants, happy enough, Adam toying with his chips, while, through the windows, we watch red-faced parents bribing children to come through the door with God knows what. Adam and I do bribes, too. But, nowadays, it's generally a calm and civilised negotiation, mainly because he has the upper hand. I'm buying, he's selling - and he knows I know that the more I push the less it's going to work.

His mother's attitude has always been different from mine - saner, you may think. Ruth's basic motor on child-nutrition issues is that ancient, atavistic one that derives physical pleasure from seeing one's darling full-up and plump, and pain from watching them go out to play or off to school underfed. With Adam, in the days when sparrows had larger helpings, her approach was generally that of Malcolm X - By Any Means Necessary. Coke? Well, it's energy. So what if he wants a McDonald's? At least he wants something, and we're putting something inside him.

She had a point. For some years, putting food in him was quite difficult. His stomach was clearly not working properly, he had wind you could measure on the Beaufort Scale: for a while his diet was mainly Infacol and gripe water. When the colic passed, he started to feed better. But he never seemed to enjoy it. In fact, food, particularly new food, seemed to frighten him.

We went to live in Thailand when he was two: Adam stuck resolutely to a trusted Western toddler's menu. Pasta, potatoes, rice, broccoli, peas, fish fingers and fried bits of chicken. An apple. No mango, no banana, nothing remotely spicy - in fact, in the four years we lived there, Adam only came to like one exclusively Asian food - a bizarre street snack called yum-yum, made of shredded raw pork sugared and sun-dried. It was a chewy, salty sweet, essentially, and Adam has never had an argument with sweets.

While we were there, though, I managed to lose his trust in me, forever, as far as food is concerned. One day at a Thai restaurant table, when he was four or five, I offered him money if he'd just try something Thai and tasty. He remembers the event well - 'the day you made me drink the fish sauce'. Stupid Dad. His reaction was spectacular - he threw up all over the table. Who wouldn't? Now, if I offer him an olive or an anchovy, a macadamia nut or a piece of 70 per cent cocoa chocolate, and tell him it's just delicious, he'll go: 'Oh, no, I don't think so! Nice try, Dad.' I'm not catching him out again. And, quite understandably, from then on Adam's ultimate defence when pushed to eat something he didn't fancy, or even to finish his plate when he'd declared he was full, was similar - gagging, retching, puking. Whether this was intentional or psychosomatic, it worked.

Many parents would say we haven't got a problem. Most can cap any story of ours with some tale of obsessive pickiness or weird aversion far more gruesome. I've met a kid who has eaten only bacon for the past five years. Several doctors have shooed us out of their surgeries: time-wasting middle-class worriers that we are. Adam's too skinny for parental comfort, but he looks fine on the growth charts. He eats less than most of his peers, but he can run as fast as any of them. Small children must be the most fuel-efficient organisms on the planet - ours can go up a mountain on half a peanut-butter sandwich and some crisps.

So why should we worry? The problems appear, and our stress levels rise, when he's been ill and his ribs show. Or, as happened last winter, when the narrow list of foodstuffs he will eat with enthusiasm actually contracts. That was a bad time. Fish fingers, chicken breast and scrambled eggs all departed the menu in the space of a few weeks, and the only meat or fish protein left was little Piglet-pink Richmond sausages. But we bounced back, with Marks & Spencer's breaded chicken goujons (that's posh nuggets), boiled eggs (yolks only) and canned tuna. You keep trying, you don't give up, you're positive, encouraging and you offer variety without pressure. You keep your temper, you try to get off his case. But how we miss those fish fingers - and I never thought I'd find myself saying that.

Other sensible people would say that the problem is mainly me, and I have to accept that. Adam's diet offends my sensibilities because I'm a food snob. I find it depressing that he wants to eat what all children do, that he wants to graze with the herd. On treats, I take my child to Burger King for chicken nuggets! Where did I go wrong? Why couldn't I grow my own little Fearnley-Whittingstall? Is it really just because I tried too hard?

I hope I've calmed down now. I accept, with sadness, that I may never eat a plate of oysters with Adam, but I have grown to respect his position. I'm proud of the way he'll fight for his diet. He wins the arguments now. He uses logic, threats and sometimes he lies - just like I do. That started when he was five, one afternoon on the street in Bangkok as we walked past a familiar yellow and red shop fascia. 'You know, Dad, how you said that you didn't like going to McDonald's, because you'd read in a book that the food's rubbish and they don't give the people who work there enough money?' Yes? 'Well I think you're right,' he said. 'But I read [he couldn't yet read] in my book that they don't put rubbish in the food and they do give the people enough money... at Burger King.' So that was where we went, and we had a blow-out. I think it was then, that afternoon, that I accepted that he gets pleasure from food. And what more could I ask?

What is true, and here lie my hopes, is the fact that he likes the idea of food, the power of appetite and particularly the fact that cooking is sorcery. A couple of years ago he realised that a wooden spoon is a wand and in front of the stove he can be a wizard straight out of Hogwarts. We started with breaking eggs and turning them into scramble. Then, muffins and toffee and home-made ice cream - all things that need a potion or a spell to make them happen. Now he'll cook up a mean spaghetti bolognaise, me sous-cheffing - complete with the magic ingredients: a splash of red wine, tomato purée from its toothpaste tube, lots of garlic. He'll taste the sauce too, and eat a full plate, although more spag than bog. And a pile of parmesan. He likes the noise of the kitchen, the flames and the knives and the crash of pans. I may never raise a Fergus Henderson, but I might get an Anthony Bourdain.

In Marks & Spencer we had a gas, racing up and down the aisles, he riding the trolley choosing and rejecting like a manic man from Del Monte. At the till we put down a Roquefort and pepper beefburger; some Double Gloucester and some Wensleydale; a punnet of apricots; Eve's apple pudding with custard, two syrup puddings, a pack of lemon mousses (we had to stop at three - he'd have taken the whole ready-pudding section otherwise), some English asparagus tips; Pink Lady apple and raspberry juice; strawberry, banana and vanilla smoothie; a pack of Arctic wild line-caught silver-smoked salmon slices (my heart swelled with pride when he reached straight for the most expensive thing in the M&S fish section); a multipack of little cheese-and-chicken-flavoured nibbles and a cheese knot bun('are you sure it's cheddar?', he asked the lady in the bakery section).

We got home and put the beefburger on the griddle. It was a shot in the dark - he's never eaten a burger, he doesn't like blue cheese and pepper is spicy, an ancient no-no. But it was his choice. 'It's good but bad too. It's not really on my side,' he said, pushing the burger aside after one mouse's bite. 'I don't know the word for it. Too sort of... disgusting.' But the asparagus was a breakthrough. 'It tastes nice and green - sort of like spring. I think we'll put it on the maybe pile.' When I told him you could smell it when you did a pee, it went up to the Yes pile, and we had more on Sunday. There was lots of sniffing in the loo.

The next day, I chopped up the smoked salmon and put it in pasta with some crème fraîche. That's my boy. He ate all his bowl. 'Yummy, and sort of chewy - a bit like not-very-cooked bacon. It's in the Yes pile.' Other items didn't go so well. Apricots: 'It's an orange peach! Huh!' They withered away unloved in the fruit bowl. Pink Lady apple and grated raspberry juice - 'It has a bit of an icy feeling, sort of like not very ripe cherries. They should put some sugar in it.' A strawberry and vanilla smoothie with probiotic low-fat yoghurt: 'They should stop it being made. They should ban it.'

The new cheeses were chosen because one was like an orange cheddar (Double Gloucester) and the Wensleydale was what they ate in Wallace & Gromit. We did a triple tasting of them, with a corner-shop cheddar, on baked potatoes. 'Hmm, like cheddar, but a little less energetic,' he said of the Wensleydale. 'Ding! Double Gloucester is wicked! High energy! It makes you want to run around a lot.' All on the Yes pile. Then we hit the desserts. Every one a triumph. Which was another breakthrough - although he has a sweet tooth, anything complex, anything 'mixed-up', generally gets the thumbs-down.

A few days after the M&S experiment, Adam volunteered to go with Ruth to Sainsbury's, on the standard supermarket run. She came back beaming. He'd never, of his own volition, chucked anything in the trolley before except for crisps. This time he'd picked out tagliatelle, some panini breads and a box of Shreddies. Happy Dad. I'm not making a booking at Nobu yet, but the dream is always there. OFM

THE EXPERIMENT
Take one fussy eater - Adam, aged 7. The bribe: allow him to choose anything he likes from a supermarket - in this case, Marks & Spencer.
The rules: he must take one item from each section, and then try at least one bite of everything. So, what did Adam Renton choose - and did it change his eating habits?

Smoked salmon slices
'It's in the Yes pile. We should buy this more -it's like bacon. What do you mean, I don't usually like fish, dad? Of course, I like fish. I love fish! '

Lemon mousse
'This pudding comes second - it's kind of lemony and nice. It's got sort of lemon pips in it - and that's not so good and that's why it's relegated to second.'

Eves apple pudding
'The apple pudding has a creamy taste that I don't like a lot. But I'd buy the syrup one and the lemon mousse again. That would put a big smile on my face.'

Double Gloucester
'Wicked! High energy! Nice and sweet like cheddar and it make my tongue tingle. It makes you want to run around a lot.'

Asparagus
'Tastes like spring. It's really cool that you can smell it when you go to the loo - a scientist would be interested in that.'

Wensleydale cheese
'Hmm, like cheddar, but a little less energetic. Sort of chalky and greasy. It makes you cool down. Quite nice. But parmesan is still my favourite.'

Strawberry and vanilla smoothie with yoghurt
'I don't like this at all. It's too much mixed up. They should stop it being made. They should ban it.'

Apple and raspberry juice
'Don't like that much - it's got bits in it. It has kind of an icy feeling, sort of like not very ripe cherries. They should put some sugar in it.'

Syrup sponge pudding
'This pudding is fantastic. It's promoted to first. They should make millions of them and everyone should start eating them - but don't eat 200 a day.'

Cheese knot (bread roll)
'It's got a cheesy flavour and a soft vinegary taste, not like salt and vinegar crisps where the vinegar's too hard. It's quite a good idea, putting crunchy cheese on.'

Apricots
'It's an orange peach! Huh! What's the point? Everyone knows what peach tastes like.'

Roquefort beefburger
'It's got a funny taste. I hate blue cheese. It's my worst food in the world. If it was a burger with hot oozy cheese I would try more. I did actually nearly throw up.'

The verdict: 'It was cool being allowed to choose, though I would have chosen a thousand billion sweets. Next time we'll buy different foods - like that meringue stuff I spotted. I don't know what I'll choose ... maybe a different fish. My favourites were syrup pud, then Double Gloucester, then smoked salmon, then the asparagus.'