"And then I'll be f---ed. It's exhausting. Hopefully I can then go and live a perfect Berkeley, San Francisco, organic, biodynamic lifestyle and have a hammock."

It's hard to imagine the 41-year-old TV cook taking his foot off the pedal, but then it's also easy to understand it would be incredibly exhausting to be Jamie Oliver.

He's in Australia on one of his regular visits here, and it's the usual whirlwind of competing elements. He's mainly here to relaunch his chain of Jamie's Italian restaurants, with a bit of promotional work for Woolworths and his television shows thrown in.

Right now, the Oliver Empire is estimated to be worth ??240 million ($417 million), with his cheeky-chappy persona and hugely accessible recipes spawning more than 30 television series and 20 cookbooks.

On Ten, there's the fourth season of Jamie and Jimmy's Food Fight Club, where he and his friend Jimmy Doherty dish up some feasts in a cafe on Southend Pier in England, with celebrity faces popping in.

He's also been touring Italy for a series about home-cooking by the nation's nonnas. Also upcoming is a book series and TV show about quick and easy five-ingredient food.

Alongside that is his continuing campaigning on issues such as better food for children in schools, sugary drinks taxes and food waste.

And then there's the masters in food nutrition at St Mary's University, London, that he expects to finish in the next two years, which is astounding for many reasons, not least that he's also dyslexic.

The person who steers all these commitments and the empire is "me", he says, and it's less of a hugely strategic operation and more of a naturally evolving range of interests.

"I generally don't do anything unless it's shifting the bar somehow. That's always the motivation," he says.

He says there have been "all sorts of f----ups and mistakes" along the way, such as his cookery schools which struggled and a direct-sales business that failed to break even. But the successes have been astonishing: he is indisputably the titan of television cooking.

This year marks the 20th anniversary of Jamie Oliver's first appearance on the small screen.

In 1997, as one of the sous chefs at the Michelin-starred London restaurant the River Cafe, he was a background player in a BBC doco about its Christmas menu. In it, Oliver is babyfaced but his distinctive skill, passionate enthusiasm and oi-geezer turns of phrase which caught the attention of TV producers is clearly evident.

But since then it's not been easy - he has regularly incurred the wrath of the press and other critics, particularly over his campaigning which has been often denounced as do-gooder meddling. How does he withstand the rough with the smooth?

"I think for celebrities, it's a bit like dog years," he says. "I've been doing this for nearly 20 years so it makes me about 100 years, and every five years the press will gang up on me and after you've been done over four, five times you start to sniff the patterns. Ultimately if you're enthusiastic and you've got an opinion, then you're always going to jar 50 per cent of the country and then the other 50 per cent will be like 'oh, this is kind of interesting'.

"Nothing I've done has ever been clever, it's always been fundamentally basic. The concept of it being right or wrong, feeding shit to kids 190 days of the year from the ages of 4 to 18, is that right or wrong? It's clearly f---ing wrong, and especially if it's provided for by the state. It's wrong - wrong, wrong, wrong.

"I think after a while, after about 10 years, you just start getting a bit battle-hardy and also, I mean this not in a cocky way because I think I'm bigger than my own boots, but you have to think bigger and more epic. You have to step back and look at the bigger picture."

Looking back over his 20 years, he says he's gathered a great team - he has a core group of 130 staff at the Jamie Oliver Group - and his continuing activism and the inroads he's making with governments and big business has never been more exciting.

"Honestly, I'm a really complicated old soul and I know obviously I would say this about myself, but I'm honest. I'm really bad at lying and I follow my heart and I think I'm just stupid enough to keep trying things and I'm just clever enough to keep winning enough of them."

WHAT Jamie and Jimmy's Food Fight Club

WHEN Ten, Sundays, 3pm