In any other country, Jamie Oliver would probably be hailed a hero. He has raised the standard of school dinners, given disadvantaged youngsters jobs in his restaurant 15, masturbated a boar (in a possibly misguided attempt to highlight porcine cruelty) and helped a feisty bunch of Rotherham readymealers learn how to cook.

But this is Britain so, instead, we slag him off as though he’s the spawn of Satan – “Oh that meddling mockney chef, sliding down banisters, riding scooters, making the nation healthy and saving the slowly but surely furring arteries of our porky teens”. Even Marco Pierre White, a man Oliver hugely respected as a teenager, called the school meals campaign “cynical” and Oliver, “a fat chef with a drum kit”.

But Oliver is over it. He says Pierre White has done nothing he respects for 15 years, although he doesn’t want to start a fight because, “He’d probably want to give me a right hook and I wouldn’t want to mess with him because he’s quite a lump.” But when even Gerard Depardieu is getting in on the act – he recently told a newspaper Oliver was “all about marketing” – you have to wonder what’s going on.

“Gerard Depardieu?” says Oliver, when I relay the French actor’s recent comment. “I know I’m a bit like Marmite to a lot of people and I completely understand that. I get emotionally attached and I have little rants and I make documentaries about things I feel are wrong or I do cooking shows about things I’m really excited about. It can all be annoying for people but all I know is the British public support me, ridiculously.”

It’s true, but it’s not just Britain that loves him. He has sold 21 million cookbooks worldwide and the last one, The Ministry Of Food, stole the best-selling Christmas cookbook crown from spoon-sucking Nigella Lawson. His TV series, Jamie At Home, helped sales of edible plants go through the roof, according to The Horticultural Trades’ Association, and when Jamie rocked up at Downing Street in 2005, with his school dinners campaign and a 270,000-strong petition, Tony Blair appeared to roll over like a Labrador and pledged £220 million in days.

“The reason I got that cash out of the British Government is because mums and dads agreed with me and that connection is a weird one.”

Right now, Jamie has a new mission and he admits it’s a selfish one – his restaurant chain, Jamie’s Italian. He already has three, in Oxford, Kingston and Bath (at which, despite the credit crunch, people are queueing out the doors, his MD tells me) and now he’s here to save Brighton from the scourge of sub- standard restaurant fare with “affordable food for the masses”.

Jamie, who is sitting upstairs at his new Italian as a man drills the finishing touches into the pasta kitchen, says his “balls are on the line” with this venture but that he’s very excited. He also says the staff, who are downstairs learning the ins and outs of herbs with his Italian mentor Gennaro Contaldo, get more training than any he’s ever had at a restaurant – “Michelin star or not”. Then he says something a bit odd: “It’s not going to be the best meal of your life.”

What?

“I don’t want it to be. I want this to be somewhere accessible and really approachable, where you can go twice a week and see a different part of the menu and I want the receipt at the end of it to not be painful.

“You know,” he says edging closer, “It’s the most incredibly brilliant thing I’ve been involved in food-wise. It’s the first time I’ve done something for me. What I’m most proud about with these restaurants is there may be six 14-year-olds with 12 quid in their pocket. You’ll have a family all dressed up, a couple of mates, and OAPs trying fresh pasta for the first time. It really is an inclusive place.”

He also admits “this was never my plan” and I think he means the whole shebang, the Jamie Oliver brand.

In 1997, Oliver was working at the River Cafe when he was caught on film for a documentary. The next day he was called up by five production companies, who realised they had hit TV gold, and before he knew it he was Channel 4’s Naked Chef.

Until that moment, life had been pretty normal – holidaying on the Norfolk Broads in leopard print swimming trunks and helping out in his dad’s Essex pub. At five years old he was cleaning out the back bins, bottling up. By the time he was eight, he “had a knife longer than my arm and I could cut like a bitch”. The pub is where his only major kitchen disaster occurred – he boiled several tins of condensed milk dry and they all exploded. “Had that happened in service I would have probably blinded about three people and scarred them for life.”

When it comes to eating, Jamie stands by his granddad’s favourite adage – everything in moderation and a bit of what you like, which is why he worries about the food split in this country. He says the middle-classes are eating better and the poorer, worse.

Then there are the families who have replaced square meals with sugary snacks and fizzy drinks. “The end of that story is we now have the first generation of kids expected to live shorter lives than their parents. It’s none of my business but then it’s sort of totally my business.”

Oliver genuinely cares, which is why when people take a pop, I imagine it probably stings more than he lets on. The day after we speak there’s a picture of him and his heavily-pregnant wife (she’s about to give birth to their third child) at a supermarket. Jools appears to be putting some shopping in their car and Oliver, who according to the magazine couldn’t care less, is letting her get on with it, which I’m sure isn’t the true story.

He says, in general, he’s “up too early and back too late” to be bothered by the paparazzi but they do target his wife. “She gets loads of grief. Both times when we’ve had our kids they’ve followed her constantly in the last weeks of her pregnancy. They’ve made her emergency stop and pestered her in the street. I know people think, ‘Tough shit. You’re famous. You deserve it’, which is sort of right. But if you don’t want to watch me on telly you have a remote control and you can use it and you don’t have to shop at Sainsbury’s and you don’t have to buy my books.”

Which is all very true. But there are plenty of people who don’t want to turn over and who do want to buy his book... including, maybe, even the Queen. When Oliver was awarded his MBE in 2003 he was “well-chuffed” and being quite patriotic he decided he’d send HRH a Christmas card, “just to say have a good one and I hope your turkey’s good”.

A few days later, the Queen’s lady-in-waiting called to say thank you – not something Oliver had anticipated when, encouraged by a friend, he left a joke message on his answer phone. “It went a little bit like this – ‘Beeeeep. Hello. Hello. Sorry, no, I can’t quite hear you. No, you’ll have to say it a bit louder. Hello? Ha! Only joking. Please leave a message’.

“Anyway, she phoned up twice and left a message. The Queen’s lady-in-waiting was going, ‘Hello, hello. Can you hear me?’ It made me cringe.”