"You know," says Jamie Oliver, sighing quietly: " I am not doing this for the money as I could have retired five years ago. I'm here because I want to speak out about things that matter – about what people eat, about preventing obesity. It's a killer."
That's why he is so furious with Michael Gove, the Education Secretary, for allowing his new free schools to sell junk food and opt out of the standards which Mr Oliver has worked so hard to get introduced into schools in the rest of the country.
"What Gove has done is a crime," he says: "He's clever – and I like him – but allowing the academies to sell what they like is risking our children's health."
He certainly has the platform: 100,000 customers a week eat in his restaurants and many UK homes have a Jamie cook book – he's sold more than 30 million books, second only to JK Rowling. Put simply, Jamie has made it cool for the young to like cooking and to care about things like healthy foods.
He knows how to make the moolah too. The young chef, 37 next Sunday, from Clavering in Essex, is ranked the 500th-richest man in the country and the world's wealthiest chef: his personal wealth is estimated at £150m. The Jamie's Italian chain of 44 restaurants is thought to be worth about £110m alone. Add three Fifteen, one Barbecoa, two Union Jack restaurants and two Recipease cafes to cookery schools as well as his event catering business, Fabulous Feasts, the Fresh Partners TV production company, which shows in 40 countries, and the cook books and you have the full blast of the empire.
Mr Oliver is taking part in a Virgin Unite Screw Business as Usual summit being held at his flagship Fifteen restaurant, hidden away off the Old Street roundabout in London. With him nattering around a metal cooking bench are Sir Richard Branson, The Big Issue's John Bird and Ben Cohen of Ben & Jerry's ice cream. Talk is about how businesses must be social creatures, how the Occupy movement has caught the spirit of our time and why products will be priced one day according to the real cost, one that includes water used, forests ruined and energy spent. It's a surreal event; a sort of new-age CBI.
We sneak off to Mr Oliver's office around the corner, full of big sinks and ovens, rolling pins, pots and pans, to chat around a chunky wooden trestle table. He's better looking in the flesh; his blue eyes are twinkly and it suits him to be lightly tanned. Even his north Essex vowels are gentler, more pukka-like. I can't help but tell him that I also grew up in Clavering, used to visit his father's pub and still live only a few miles away, know some of his family and sometimes spot him shopping at Humphreys, the local butchers. He seems delighted to meet a fellow villager and we joke about the eyesore of a radio mast a relative of his has in his garden. But when I ask why he hasn't opened a Jamie's Italian in our town – Saffron Walden, where he's the boy made good – you get to see his steely business side: "I've done the numbers. It's a lovely town – there's lots of money but people don't like spending on eating out; they like their set prices. Ask is about the most they will pay! But we might open a Union Jack – the new restaurants which are aimed at the smaller market towns like Walden."
His non-sentimentality is a clue perhaps to why Mr Oliver has been so successful where other celebrity chefs have failed: cash management is strong, discipline is tight, each project is run to strict targets and he hires professionals. If Jamie is the creative side of the Oliver brain, then John Jackson, his chief executive, is the right side; he worked with the Roddicks, Mr Bird and Branson before joining Mr Oliver five years ago.
Since then turnover for Jamie Oliver Holdings has shot up from £12m to £200m this year with pre-tax profit forecast at between £25m and £30m. The group employs more than 6,400 people, 250 of whom are in the head-office, and 2,900 in Jamie's Italian. It's a punishing formula: each new Jamie Italian costs around £1.9m to create and each employs 110 people. But they make money the minute the doors open and cover costs in two and a half years. Not bad in a sector where the failure rate is about 98 per cent.
Mr Oliver says the public, while they love eating out, are being more careful about how much they spend – hence the roll-out of the lower-priced Union Jacks restaurants.
His big beef about the Government's attitude towards promoting healthy food for kids is that in the long term not looking after their nutrition will cost the country more. It's bad for business: "The long-term cost to the country and the NHS runs into millions and millions. In 20 to 30 years diabetes, linked to obesity, will be the biggest killer of all. The Government is bonkers. Do you think those clever people at the Department of Health meet for tea to chat to the people at the Department of Education about this?" You know his answer.
Playing games with children's health is also why he believes the Government is mad not to tax "crap" foods as it is doing with minimum pricing for alcohol; why schools should be forced to have cookery classes and teach children about nutrition.
His role is being the "the provocateur, the renegade", he says, and whose message will be louder and last longer than the food establishment which wants to sell cheap. As he tartly points out, he survived 12 years at Sainsbury's, a period which saw three chief executives come and go, before he lost his lucrative contract last year advertising healthy foods.
There's more subversion this weekend with the Jamie Oliver Foundation's Food Revolution Day to "mend the relationship with food which has broken down", he says. Foodies, chefs, parents, schools and companies will be out in force banging the drum to put food education back into our schools and workplaces.
He may be socially driven but is not a fan of charities: they are "disempowering" – I think he means bollocks but is being polite. "Most charities are badly run. Even my own is a pain and I wish I had never done it. There is so much administration, so many particulars to attend to. My experience is that it's better to run your business well and treat people well."
You know what? It's not often I believe people when they say it's not about the money but with Mr Oliver I do. More fascinating, perhaps, is to know where his drive comes from. Part of Mr Oliver's stardust is that the public trusts him and thinks they know him – as they do with Branson – so the challenge now is whether he can transfer that personal trust from the man to the brand to get an even louder voice.
Can he do it? Mr Oliver pauses for breath, not something he does often, smiles his sweet smile, and says: "I don't know." I wouldn't bet against him.
Route to the top: Rise of Jamie Oliver
Jamie Oliver was brought up in Clavering, Essex, where his parents still run the Cricketers pub. He went to Newport Free Grammar School, leaving at 16, and studied for a City & Guilds NVQ in home economics from Westminster Kingsway College.
His first job was as a pastry chef at Antonio Carluccio's Neal's Yard restaurant, getting on well with the man he considers his mentor, Gennaro Contaldo. From there he went to the River Café as a sous chef, working with Ruth Rogers, wife of the architect Lord Rogers. It was here that he was first noticed when appearing in a BBC film in 1997, making his presence known and unscripted, in a documentary about the café. The rest is history. His show The Naked Chef was shown later that year, and his cookbook went became a number one best-seller. He is married to Jools, a former model who is designing a range for Mothercare, and they have four children. Weekends are spent in Langley, close to where he grew up.