A life class

But perhaps the most significant first for the painter was that he had made a name for himself. Finally, he was better known for his portraits than for who his father was: Tory minister Tim Yeo. When, in 1994, it was revealed that Tim had fathered a baby by his mistress, Tory councillor Julia Stent, his family was thrown into the media spotlight. Tim was forced to resign as environment minister (at the same time it also emerged that he had fathered an illegitimate child previously, a daughter who was adopted at birth, from his time as a student at Cambridge).

At the same time, Jonathan, who had only been taken into his father's confidence within hours of the scandal hitting the headlines, was fighting for his life. He had Hodgkin's disease, a malignancy of the lymphoid system (he has since recovered, although doctors will never give him the all-clear). On the same day that news broke of his father's love child, Jonathan was told by his doctors that the chemotherapy he had been undergoing had only partly worked and he needed radiotherapy.

'All this was going on at the same time,' he says, still looking shaken by the memory. ' Suddenly the whole world was slightly different from how it had been before.' He found himself hounded by reporters and TV crews outside his parents' house. It was a 'depressing' time for all his family.

At this point, he leaves the room to get another espresso. On returning, minutes later, he says, sounding stronger: 'I think that whenever you have weird things in your life to deal with you just get on with it. If you get ill young, you tend to be much more optimistic about things. You believe you're going to get through it. But even so there is a bit of you that has to acknowledge you possibly won't.'

What kept him going then was the thought of his younger sister, Emily, who, five years earlier, at the age of 15, had collapsed at the breakfast table with a brain tumour, leaving her paralysed down one side. The family were told to expect the worst. 'I had to go through my last year at school thinking she wasn't going to be around for long,' he says. 'After that, my illness, and everything else that has happened to me, seems much less emotionally draining.' Although still disabled, Emily recently married. 'Thankfully,' he says, 'she's still around.'

The same day Jonathan found out he had Hodgkin's disease, his father, who is MP for Suffolk South, was made a Cabinet minister. Jonathan was 22, in his final term studying film at Kent University. 'In retrospect it was very obvious,' he says. 'I had all kinds of symptoms, like eczema, that I'd never had before. But each one was treated in isolation.' Then he discovered a 'large lump' in his neck. On closer inspection, his mother, Diane, marched him off to the same doctor who had treated his sister.

He found the best way to cope was to launch himself into a frenzy of painting. 'My work became my focus and it was a fantastic thing in retrospect,' says Jonathan, who failed A level Art. 'Before I got ill I used to think I didn't deserve to have a cushy life being a painter. I felt I should get a proper job that I could earn a living out of. Then you think, "F*** it, just in case I'm not going to be around very long, I want to spend my time doing what I enjoy doing". For the first time in my life, I stopped thinking about what I was doing from everyone else's point of view and just thought about what I wanted to do.'

He lost his hair and had to wait three days after each hospital visit before he felt well enough to pick up a paintbrush. The only way he found he could keep the nausea at bay was to smoke copious amounts of dope. But his determination paid off. Halfway through the chemo and radiotherapy, he put on an exhibition and sold all 25 of his paintings, including a portrait of Archbishop Trevor Huddleston, one of the founding fathers of the South African antiapartheid movement.

'Maybe if I hadn't been ill I might not have had the determination to do this sort of job,' he says. 'To get ill is obviously not the way you'd choose to have that happen but I'm very glad I did.'

Now, his check-ups are once a year. 'You forget about it completely then something reminds you,' he says. 'If I get anything wrong with me the doctors all panic. You always have to be on the alert and that's annoying. It should be out of the way now. I should be allowed to get on with my life.' His energy levels fluctuate, propelling him out of bed by 6am some days and into a deep sleep by early evening on others. Most days, he is at his easel by 9.30am. 'You have to treat it like an office job,' he says, 'if you want to get lots done.'

These days, he can pick and choose who he paints. He recently completed his second advertising campaign for jeweller Theo Fennell, featuring baubled women cavorting naked. He has just finished two portraits of Ivan Massow, the debonair millionaire founder of one of the first UK companies to offer insurance to gay men, who was once mooted as a Tory candidate for London Mayor. The impressive portraits sit side by side on his mantelpiece; one of a fat Massow, the other a slimmed-down version. 'Ivan wanted to call it "Being Geri

Halliwell" says Jonathan, with an impish grin. 'We started it two years ago when he was a bit unhappy and overweight. Then he dieted and worked out.'

A nude form that frequently pops up in his portraits is that of his actress and model girlfriend, Shebah Ronay, who played Natasha Anderson in Hollyoaks. The 30-year-old daughter of designer Edina and granddaughter of the restaurant critic Egon, is now a film critic. They have known each other since their schooldays - she was at More House, he at Westminster --but only became a couple a year after Jonathan became ill. She helped him rethink his lifestyle.

'I don't go out caning it like I used to,' he says. 'I don't feel I've got to do everything in the next six months. I'm better at taking a long-term view.'

Jonathan shared his 30th birthday with TV presenter Jamie Theakston, but he and Shebah are, on the whole, remarkably low-key for one of London's It couples. 'We used to go to a lot of premieres and celebrity parties but you quickly realise that you see the same people, have the same conversations,' he says. 'It's very shallow. Shebah got quite down about it but she's much happier now.' They share a flat in Pimlico, in the same block as Jonathan's parents and sister, but as yet have no plans to get married. 'I've always reacted slightly against what my parents did,' he says. 'What's weird is that quite a few of my friends have been married and divorced in the time we have been together. I just think our generation is a bit more cynical.' He is looking forward to starting a family of his own one day soon, however, which might send him up the aisle. 'I think it's fairer on kids,' he says, somewhat reluctantly.

'I suppose I've had more evidence than most people that you can't make definite plans,' he says, sounding decades older than his actual years. 'You can have a vague idea of where you want to get to and move in that general direction. But it's very dangerous to make real commitments. Then you can't adjust to things and something always comes along to blow your plans out of the water.'

Journalist Giles Coren, a friend since Westminster, says 'Jonny' surprised everyone by becoming a talented painter. 'You just thought he was a bit of a waster,' he says, jokingly. 'He's a great schmoozer which impresses the kind of people who buy his paintings. He's not fazed by any level of celebrity. He's not unlike his dad --funny, cool, and naturally charming.'

Although he has always resented being defined by who his father is, Jonathan is grateful: 'I think there's a slight sense, having successful parents, that you're brought up in a culture where you expect to succeed.'