Fergus Henderson: The hip hogtelier

Fergus Henderson doesn't look like a successful businessman. With his portly frame, little round glasses and violently striped suit, he looks more like Billy Bunter. 'It's made from a butcher's apron,'he says, delighted. 'One of the barmen at St John made it for me. I don't normally look this natty.'

But appearances can be deceptive. Fergus, 47, is probably this country's most influential chef. His 'nose-to-tail eating' philosophy revolutionised British cuisine and introduced a new generation to the delights of bone marrow, gizzards and chitterlings. His eponymous restaurant on St John Street in Clerkenwell is consistently voted one of the world's best and, 17 years after it opened, hasn't lost a crumb of its zeitgeisty appeal. Meanwhile its little sister, St John Bread and Wine, which opened in Spitalfields in 2003, has become the canteen for Tracey Emin and the East London art crowd. And now there's a hotel, four years and £6 million in the making, joining the stable.

The St John Hotel will be housed in what used to be Manzi's fish restaurant, opposite the new W London hotel on Leicester Street. It will offer a restaurant and 15 minimalist rooms, with whitewashed walls and green floors - a rare venture into colour for Fergus and his business partner Trevor Gulliver, 57, who believe that a restaurant's décor should consist purely of its diners. 'It will be like sleeping in a pond,' Fergus shouts above the racket of clattering china and crashing bottles in his restaurant.

'The last thing I want is St John outlets all over the place,' he says, but having travelled the world on wine-buying trips and a televised eating odyssey, he learned exactly what he wants from a hotel - and what he doesn't. 'I was staying at this fantastic place in Tokyo. The room was absolutely enormous, the bath could have fitted four people and one wall was all window. And I felt so lonely, I was absolutely miserable.' Rather than chilly grandeur, he believes the secret to a good hotel is a certain saucy quality. 'Of course, we don't want to encourage guests to do things they shouldn't, but it would be nice if it gave you the feeling that you might be joined by someone' There is much sauciness, too, in the fact that the baths sit inside many of the bedrooms, 'so you can watch telly if you're on your own, and talk to the person you're with if you aren't. Of course, we've blocked off the loo so you can poo in private,' he goes on. The floors are rubber, 'so it's easy to wash away the sins of the night before.'

'We will have a dialogue about a chair, or how you walk into a room, that can last six months,' says Gulliver, a smaller, chattier and less flamboyant version of Fergus, who describes himself, eyeing Fergus's suit, as 'more of a tweed man'. The restaurant will stay open until 2am and offer St John-style food, with some concessions to home-from-home cosiness. But not too many. 'Some people say our food is challenging but they are fools,' barks Fergus. Even the contents of the minibars has been subjected to exhaustive existential analysis. At St John Hotel, they will be filled with esoteric bottles such as Vieille Prune brandy, Poire William eau de vie and Lagavulin whisky, but the only chocolate on offer will be Toblerone. 'It has a hair vest quality. You take the first bite and think, "Whoo! I'm in my hotel room!"But then it hurts the roof of your mouth and reminds you not to get too smug and cosy.' That is the only hair vest aspect, however; overall the plan is to 'love you and stroke you in the midst of the urban turmoil'.

Initially, Fergus's plan was to open a hotel in the intense urban turmoil of Beirut. 'I had this idea of being like Humphrey Bogart in Casablanca, in my white dinner jacket, but doing what we do here.' Politics, and a property developer with plans for a tower block on the chosen site, intervened. 'But by that stage the seed had been sown.' Then the Manzi's site came up. The fish restaurant had featured largely in both Fergus's and Trevor's childhoods; Fergus fondly remembers meals there of chips, peas and scampi, as well as the 'pretty disgusting' cucumber salad that his father, Gatwick Airport architect Brian Henderson, always ordered. Meanwhile, for Trevor, whose father was in the Flying Squad, it was 'the home of bent coppers', and the place he went for fish and chips after pantomimes. 'If Manzi's had gone to somebody else and become a Nando's or another Chinese restaurant, something would have been lost,' he says.

Initially, the pair looked for finance from hedge funds. 'I've never met a bigger bunch of unpleasant people,' says Fergus, choking back the epithet. In the end, they dumped the financiers and approached friends and fans of the restaurant, including the artists Tracey Emin, Peter Doig and the gallery owner Sadie Coles. 'They were brilliant, they just said, "Oh yeah, sure,"and they didn't mind how long it took. They've been lovely to us.' Why do modern artists love him so much, I wonder? The late Angus Fairhurst once said that it was because St John has no art on the walls, 'which is very good for artists. You don't want to be put off your dinner by looking at somebody else's art'.Fergus is protective of his glamorous investors, wriggling uncomfortably when their names are mentioned and refusing to be drawn further.

Did the credit crunch make them doubt the wisdom of the project? 'Well, we opened St John in a recession,' he says, unworried. 'We're obviously drawn to choosing the wrong moment.' Anyway, the hotel is bound to be a success. Trevor has shown Nick Jones, founder of Soho House, around. 'He said "You'll do loads", which is a technical term I believe,' he jokes. 'Of course we need to make a profit. It's quite important to be good at what you do. But we're not a brand, and there isn't a plan for more.'

So why do it in the first place? 'It's nice to keep busy,' Fergus says rather vaguely. Still, he might well have remained simply the head chef of his restaurant (albeit an absurdly successful and popular one) if he had not been diagnosed with Parkinson's disease in his mid-thirties. Initially, the condition gave him arms that flailed uncontrollably - never a good thing in a kitchen full of sharp knives and boiling pans - forcing him to stop cooking in 2003. By 2005, his condition had degenerated to such a degree that he was unable to eat by himself, so he underwent an operation to have electrodes implanted in his brain. This restored control of his limbs, but his speech is slurred and he finds writing impossible, let alone cheffing. 'I do miss the hands-on cooking, but I'm not very much use in the kitchen. Now my chefs are all much quicker and younger than me, and my vanity makes me a bit cross. That's driven me on to do these other things,' he says. 'Parkinson's has been a bit of a kick up the bum. We all have to think about the end at some point.' Does it ever make him feel depressed? 'Lunch puts things in perspective.'

Food is his principal recreation as well as his work. When you ask what he does away from the kitchen, he rhapsodises about Ikeda, the Japanese restaurant on Brook Street - 'Unprepossessing place but it's yum!' - and Sweetings fish and chip restaurant in the City, which is where he proposed to his wife Margot, a New Zealand-born chef who runs the Rochelle Canteen in East London (he is so uxorious that his friend, the choreographer Michael Clark, calls the couple 'Fergot and Margus'). He is also a fixture at The Groucho Club but shrinks from showing off about his social life or his friends, who, as well as the (not so young) YBA crowd, include numerous fellow chefs such as Jamie Oliver, Giorgio Locatelli and America's fiery offal-eater Anthony Bourdain, who calls Fergus 'the most influential chef in the world'. While quarrelling with each other, they seem to be united only in their admiration for him. 'I don't have time for feuds,' says Fergus, 'I don't have a feud in me.'

The couple live in his parents' former flat in Covent Garden with their three 'galumphing' children, Hector, 17, Owen, 15, and Frances, 11. You might assume that he has brought them up eating duck hearts and sucking the marrow from bones but he says that they eat a great deal of pasta because he likes grocery shopping at Camisa, the Italian delicatessen on Old Compton Street. 'I had this fantasy that I would introduce them to langoustines and we'd all sit around a huge table like something out of a Francis Ford Coppola film, but it doesn't work like that. They get bored and want to go off with their mates. But Frances is my great hope,' he says. 'She asked me to take her to The Fat Duck just after Christmas and she sat there for four hours. She loved it.'