Fergus Henderson's reaction to the devastating news that he had Parkinson's disease was to go and have a good lunch. "Being diagnosed wasn't the best moment of my life," he explains, nonchalantly.
"But good food and a few glasses of wine always put things into perspective. I'd arranged to have lunch with old school chum because I thought that my trip to the hospital that morning would be a half an hour appointment and then I'd be out again."
In fact, Henderson's limp and the strange tendency for one arm to float into the air as though he was "John Wayne on horseback", as he describes it, were classic symptoms of Parkinson's disease. There followed three days of tests. "It was weird," he recalls. "I felt fine except for this strange John Wayne arm, but the nurses were telling me to put my pyjamas on and get into bed."
Various exercises involving moving his arms and legs, plus a series of blood tests and brain scans, revealed that the owner of the celebrated St John restaurant in Clerkenwell, London, who was then just 32, was indeed suffering from Parkinson's.
The disease's chief effect is to kill off or render inoperable the cells responsible for producing a chemical known as dopamine, which allows messages to be sent to the parts of the brain that co-ordinate movement. A tremor in one hand is the first symptom for 70% of people with the condition. Sufferers can also experience slowness of movement, known as bradykinesia, and stiffness. These symptoms can become progressively worse over many years, so that even the most basic movements require a tremendous effort to perform.
In most cases, drugs are prescribed to increase dopamine production. But as these drugs can have unpleasant side effects such as nausea, Henderson decided not take them. As a young man running a busy restaurant, with very little experience of illness, Henderson loathed the idea of being dependent on drugs for the rest of his life. "It just wasn't in my nature to take pills," he says.
Younger Parkinson's sufferers often suffer dyskinesia - "your arms start flying around everywhere", he explains. "It rather got in the way of lunch." In Henderson's case, this means, of course, cooking lunch rather than just eating it. "Eventually I had to step down and hand over to my head chef, which was a bit sad," he says, with what you suspect is massive understatement.
"My body misbehaviour began to accelerating," he remembers. " It was terrible going to cocktail parties - for some reason six o'clock was particularly bad. My arms were knocking drinks out of people's hands or landing on ladies' bosoms. You feel very foolish and it's so difficult to explain: you can't say you've got Parkinson's because somehow people feel like they've given it to you. They don't know how to react. The only time I would mention it was with taxi drivers - 'Oi, are you drunk?' they'd ask, and I'd say, 'No, I've got Parkinson's.' They'd just mumble, 'Oh, sorry guv'nor.'"
Sitting in the post-industrial airiness of his restaurant, surrounded by a handful of late lunchtime customers, Henderson drinks an espresso and a Poire William ("Sure you won't have one - guard against the wet?" ). With his half-rimmed glasses, artisan's jacket and thoughtful, self-effacing manner, Henderson (43), is far removed from the big-mouthed, big-egoed celebrity chef. Instead he has the manner of an academic, searching for exactly the right word as he describes his experiences.
His gift for the charming understatement makes the fact that he narrowly missed seeing his life destroyed by this cruel degenerative disease all the more touching. Eventually he was persuaded to take the drugs, but shortly after Henderson finally accepted that he would have to endure a lifetime of taking medication, his GP suggested he consider a revolutionary treatment called deep-brain stimulation. This is an operation - performed on very few people at the time - that corrects the way in which a brain with Parkinson's creates the electrical signals needed to control the rest of the body.
The operation is performed with the patient fully awake. Henderson's head was clamped into position and two holes were drilled into the sides of his skull. "You hear the drill - like the dentist's only worse - and then there's the sound of them scraping away to make the holes big enough," he explains. "You can feel them tugging away at the membrane over your brain, which is quite tough."
Henderson's surgeon at the National Hospital for Neurology and Neurosurgery was Professor Marwan Hariz. The procedure focuses on the basal ganglia, the part of the brain that is concerned with movement, and stimulates it with electrodes. It's carried out without a general anaesthetic because being fully conscious allows the patient to report back to Professor Hariz on the effect the electrical stimulation is having. "The best way to monitor the brain is to ask the patient - there is no machine that can do it as well, " he says.
Previously, surgeons would simply burn out the defective brain cells but this procedure was risky and not always well targeted. "Now we use an electronic stimulation to block out the 'pathological traffic', in other words the electronic brain signals that are causing the shakes. It's a bit like jamming a radio signal," explains Professor Hariz. " Occasionally people see and hear things during this experience."
"I heard whale music," says Henderson. "You feel strangely calm - you think 'Ok, my head's in a clamp so I'm not going anywhere.' Just the nurse squeezing your hand is amazingly reassuring."
The second stage of the operation involves implanting a pacemaker - usually in the chest wall - which sends regular electrical pulses to the brain.
Henderson is quick to acknowledge in his dry, laconic way, the gruesome irony of his having made his name as a chef in part via his enthusiasm for offal. He has always been a dab hand with the butcher's knife and regularly serves brain in his restaurant - now suddenly someone else was taking a knife to his own grey matter.
Henderson is now back at work in the kitchen and keen to promote the benefits of DBS. He is backing an appeal which aims to raise awareness and funds to allow more sufferers of Parkinson's to undergo the operation and to increase its availability on the NHS.
The Parkinson's Appeal for Deep Brain Stimulation was founded by Lyn Rothman, a former Aids fund-raiser whose husband suffers from Parkinson's. " Parkinson's doesn't usually kill its victims, but it kills their way of life," she says. With support from friends such as the late Simon Sainsbury, she has raised nearly £3.5m and needs just a further £300,000 to establish the charity and to help make DBS more widely available on the NHS. "Fergus was very pleased to help us with this appeal - and because his restaurant is a favourite among artists, people like Antony Gormley and Rachel Whiteread have also offered their support, which is wonderful," she says.
Fergus Henderson is also surprised and touched by the interest and support that the appeal has generated, and is greatly encouraged that the number of patients benefiting from the treatment - just over 130 have had it so far - will increase. "Three years on and I'm back to normal," says Henderson. "The way I look at it is that they drilled into my skull and now I can cook again."
In support of the Parkinson's Appeal, 24 works of art by young artists will be auctioned at Christie's, 8 King Street, London, SW1 (020-7839 9060) on October 16. For information visit www.parkinsonsappeal.com