JAMIE OLIVER needs to eat. He hasn't even arrived for his interview yet, but one of his assistants is relaying via mobile phone the fact that the celebrity chef is hungry to another assistant, who is waiting with me in a colourless, top-floor meeting room overlooking the London Eye. As several lunch options are suggested and then rejected, the tension mounts. Am I about to witness a diva moment from Oliver before I've even met him? Fearing the worst - say, a demand for the spitting-hot head of an organically reared pig, with a fresh apple in its mouth from a specific stall in the Portobello Road market - I am relieved by the eventual outcome: a couple of sandwiches from Pret. One with salted beef if possible. A bit of fruit. And some water.

While the food is fetched, Oliver strolls through the door dressed in an ultramarine vintage Adidas tracksuit top. Classic Oliver togs. He looks fitter and leaner than he does in Jamie's Ministry Of Food, his current Channel 4 TV series. This is the result, he later tells me, of recently shedding a stone and a half. "Do you mind if I eat?" he asks, reaching for a sandwich. "I know it's completely rude. Now, you're gonna have one, too, aren't you? Take the one you'd like, and I'll take the other."

I'm easy. Honestly.

"Well, let's share, be Mediterranean about it."

As we tuck in to our bread, meat and water - it might come in a box, but this is ascetic fare for central London - it strikes me there is something Biblical about Oliver. It's not just that the 33‑year‑old has an angelic, boyish face with "trust me" written deep into his baby blue eyes. It is his uncanny ability to command the attention of the people around him, and to make strangers take an instant liking to him. This includes those, like me, for whom Oliver's natural charm doesn't easily translate on to TV. When he first appeared on our screens, in The Naked Chef back in 1999, I was, I tell him, one of the viewers who found him a turn-off. In fact I found his pukka, mockney schtick and smart-arsed celebrity lifestyle bloody irritating.

"You're talking as if you've changed," he says, laughing.

Well, yes. But at first I was sceptical because of, you know "The whole celebrity chef' shit?"

You could put it that way.

"I'm kind of the same, really. It's terrible to say it. But I don't blame you. So what changed your mind?"

As with many people, my turning point was Jamie's School Dinners. That series showed a young man using his fame and wealth to try to make a genuine difference to a serious social problem, namely the appalling standard of food being fed to the bulk of Britain's youngsters at school - turkey twizzlers and all. Jamie's School Dinners tapped into the zeitgeist of a country appalled by what it was doing to its young, horrified by the timebomb of rapidly growing childhood obesity, yet feeling powerless to do anything about it.

To try to sort things out, Oliver "got in amongst it", visiting school canteens, council leaders and parents' homes to demonstrate that cheap, healthy cooking in bulk, whether in the home or at school, was achievable and affordable.

Having made a dent in one crisis, Oliver now finds himself in the midst of another. Since School Dinners, he has taken his gospel of decent, freshly made, affordable food for everyone into his latest project, Jamie's Ministry Of Food. And, as if guided from above, his timing is immaculate.

"There was no recession when we started filming, but now the whole world's gone bonkers. The thing about food and recession is that people tend to buy the same stuff but trade down to cheaper alternatives."

His advice to cash-strapped shoppers? Leave those value bangers in the freezer. "Why are cheap sausages cheap? Why, because there's less meat in them, sir. They're full of rind, gristle and fat - and that ain't good for you." So there is really only one alternative. "Being able to cook a stew, soup, a curry, some baked dishes you can live pretty good as a family of four for 60 or 70 quid a week - if you can cook. And if you sit down for 10 minutes once a week and think about it."

So Jamie's Ministry Of Food is about teaching people how to cook. That's the easy part. The hard part is getting people to teach each other. The drama that propels the TV series is Oliver's attempt to get a class of 12 disciples, most of whom had never before cooked in their lives, to pass on the recipes they have learned to their mates, who should then pass them on to their mates, until, by ripple effect, the whole town of Rotherham ends up cooking. Rotherham, in South Yorkshire, was chosen because it is, Oliver says, "the most statistically normal town in Britain". It is also the place that saw fierce resistance to his School Dinners project.

Needless to say, things go badly until, in last week's show, Oliver takes drastic action. He persuades council offices, schools and businesses to send workers over to a huge hall where his disciples will demonstrate a simple beef stir-fry to small groups, who then "pass it on" throughout that day until 1000 people have learned the recipe. Whether that 1000 then pass it on further, or just forget about it, remains to be seen.

"We're not saying it's perfect," he says. "It's only as perfect as the people who participate. But what's quite magical is that one person can really make a difference."

The original Ministry Of Food was set up nearly 70 years ago by the government to make sure the population could feed itself during wartime. It saw armies of women trained up and dispatched to teach families how to make the most of their rations, backed up by a slick PR campaign. "It served its purpose very beautifully in war," says Oliver. "It wasn't saying, Well, you f***ing come to us and we'll sort you out.' It was, We'll come to you, and we'll help you sort yourself out. And we'll do it in the workplace. We'll do it in clubs. In bingo. We'll do it in the high street. In markets.'"

But if it was such a great idea, what went wrong? How did we end up being a nation that can't cook? "Well, six years after the war, rations were still in place and people were f***ing sick of it. Sick of being told what to do because it wasn't relevant any more. So the ministry was shut down pretty quickly."

That was the beginning of the rot. Then came the devaluing of dinner ladies and the emergence of a "shit and irrelevant" home economics school syllabus. Oliver's analysis of what went wrong is chef-like, with roughly chopped-up ideas thrown like ingredients into a mixing bowl. "Private tendering for school meals. Packed lunches. Junk. Brands. Freezer vans. Microwaves. Accountants. Pre-packed, pre-portioned, controllable, sit-on-the-shelf-for-a-long-timeable " Hang on, is the public face of Sainsbury's about have another go at supermarkets?

He changes tack. "Something that became clear when I was making this programme, and it became more obvious as I went further north - I hate to say it but it's true - is that to have a vision of a family sitting around a table with a meal that is tasty, abundant and cooked from scratch is considered a middle-class, elitist thing to do. And I thought, F***ing hell. What has happened in the past 30 years?' Because it was always poorer people who came up with the great recipes. The noble cooking was f***ing awful, always the same shit like boring fillets of steak. It was all the geezers cooking up the poorer' bits like the briskets and the shanks who were really kicking arse."

So Jamie's Ministry Of Food is his attempt to put things right. But the project surely needs more muscle if it is to succeed. Should Gordon Brown take it up? "I can't see that being anything but a win-win. I think the actual bricks-and-mortar bit of the Ministry Of Food is really replicable," by which he means the setting up of centres where people can pass on cooking skills. "A lot of local authorities have got this cash and you'd be amazed how many haven't got a f***ing clue what to do with it. A lot of it is spent on cheesy, shitty, irrelevant, badly printed, badly worded marketing about how bad everything is - but no f***ing solutions. Obviously I don't believe for a minute that the government will actually start a new ministry of food - that's kind of why we made our one, really."

What about the Scottish government's plans for free school meals for all five to seven-year-olds? "I think it's a bloody good idea. Because when they're young they are malleable and open-minded. And if you have 100% uptake, then there are no kids with packed lunches. Of course, what's got to happen is great training. Frankly, even if you've got a shit kitchen, if you've got a girl in there who's well-trained, they'll get amongst it. They'll have hot food on time."

His admiration for government initiatives is one thing, but Oliver's real Scottish passion is natural produce.

"We buy a lot of stuff from Scotland for my restaurants." For example? "All our beef. Shitloads of game. Lots of wild mushrooms. A huge proportion of lobster, langoustines, scallops from Torridon. The quality is great. A lot of that seafood depends on good, clean, cold water. When you go Barcelona and everyone's jerking off saying how amazing the seafood there is, you just have a little whisper and ask: So where did that come from, then?' and they'll say, Scottish. It's Scottish langoustine.' I find it amazing that a lot of Scottish people don't realise what's on their own doorstep."

Oliver's abilities with food are not, he insists something he was born with. "I was a kid who always did very badly at school. I'm realising that now when my daughters are reading and spelling words like elephant' which I couldn't even do at 12 - and I'd probably still get wrong now. But I remember when I was about 10, I started and finished my first Sunday dinner. It was a roast chicken with trimmings. And the reason I could do it was I grew up in a pub where I saw shit going on all the time. I started cooking at eight."

The pub was the Cricketers in Clavering, Essex, owned by his father. Did his dad encourage him? "Well, I wanted pocket money and he wouldn't give it to me. If you want pocket money, you work for it,' he said. So it started at 50p an hour and then eventually I got promoted to £1 an hour or something. There's not much difference between knowing how to use a knife and a peeler and getting comfortable around food. So by the time I was 10 I could rattle through potatoes, carrots, parsnips, parboiling ...

"I remember cooking my first meal. My dad checked it was all cooked properly and then we ate it, and Dad said, That was really good son, thank you, that was a really good meal.' It was my first realisation that I could be good at something and the hairs on the back of my neck went up. It makes me realise, with my own kids now, that giving positive feedback is really important - because you do remember it. I think all humans want to do whatever they get admiration for. With some kids it is football, with me it was cooking."

By the time Oliver was 14, he was put in charge of trainee chefs in the pub kitchen. "Imagine being told what to do by a 13 or 14-year-old kid when you're a cocky 20 or 21-year-old and think you're great. I had to immediately devise a way of teaching that wouldn't get my head kicked in, which was basically about letting them think they found out how to do stuff." It's a technique Oliver relies on still, whether he's trying to win the respect of dinner ladies, train students at his Fifteen Foundation restaurants, or teach hard-bitten miners how to make a stew.

Oliver insists his hard-working, well-motivated family was "working-class" before his dad bought the pub. Having "working-class" roots matters to Oliver. Perhaps this is because he is sensitive to accusations of hypocrisy since he started his campaigning in state schools. After all, his current wealth is around £25 million. He drives a luxury Range Rover. And he sends his own kids - Daisy Boo and Poppy Honey, with another one on the way - to fee-paying, private schools. "I would prefer them to be in comprehensive schools, but they're both in private schools. I have a problem with that, but my wife doesn't. The reason why I let her get what she wants has more to do with the fact of me being a recognisable face and possibly controversial. The schools that mine go to do have extra security, and they have other kids from similar backgrounds, and so neither of my kids is the one that sticks out.

"Kids want to be like all the others. My Poppy said to me three weeks ago: Daddy you embarrass me.' And that's f***ing horrible. You just want them to think you're cool and love you. So I said, Why?' And she said, All the other girls are looking at you.' It's not even because these other kids think I'm an arsehole or think I'm nice, it's just because they recognise me. And kids just want to be normal, you know.

"I am personally gutted because I went to comprehensive school But when you're in my position you don't have a life without things like death threats and horrible letters and things that worry you. Have I ever had letters that talk about doing stuff to my kids and my wife? Yes, of course I have, and that f***ing worries me. If you come to my house it's like silly glass, silly locks, silly cameras. It's slightly paranoid but I mean, f***, what can you do?

"That's the thing about living in the public eye. I think if anything makes me stop reasonably soon it will be my kids."

So is he seriously thinking about giving up the TV work?

"Yeah I might have to soon."

What would he do instead?

"I'd like to work behind the scenes. I know that's hard to believe because I'm a gobshite. But I've never been a jealous person. I'd love to bring other chefs to the forefront and lend them my experience. I make my own telly, have done for several years so I'd love to make telly for someone else, f***ing love to. I know that the lens is able to communicate with 3.8 million people. And I'm good at that. I'm good at wearing my heart on my sleeve. But if I just had a pub and had my locals I think that would give me just as much, if not more, fulfilment."

Among his plans is a restaurant in Glasgow, something he has tried and failed to get off the ground in the past. So why not try somewhere else, like Edinburgh? "I love Edinburgh. I think it's beautiful but I just think Glasgow is great. It's more Scottish, in a way."

Before he departs, Oliver hands me a bag of food with a recipe inside. It's my exhortation to pass it on'. I can't take it on the plane back to Scotland so, like a true disciple, I hand out bits and pieces on my way across town to people who look like they could use it. The Jamie Oliver effect seems to have worked on me. Indeed, if motivation were an edible commodity, I suspect Oliver could feed the five thousand.

Jamie's Ministry Of Food, Tuesdays, 9pm, Channel 4. Jamie's Ministry Of Food: Anyone Can Learn To Cook In 24 Hours, is published by Penguin, priced £25