Clarke's, 122-124 Kensington Church Street, London W8

For 23 years, Sally Clarke told customers what to eat. She's mellowed now, but are we spoilt for choice?

How reliable are artists when choosing restaurants? Does their eye for texture and composition – for balancing different components – help when it comes to judging food? Picasso was a frequent visitor to Paris's grandest restaurants, and would often pay by doodling on a napkin, but he is the exception rather than the rule. Andy Warhol, with his predilection for tinned soup, seems more typical of the breed.

The reason I ask is that I don't think I've ever been to Clarke's in Kensington without seeing Lucian Freud at his usual table. It's his local canteen. He enters at about 1.15pm and leaves at 2pm. Whenever I see him there, I'm filled with envy. Being able to lunch at Clarke's every day is surely the best perk of selling your paintings for £17.2m.

By any measure, Clarke's is one of the finest restaurants in London. Started by Sally Clarke in 1984, it has become famous for its straightforward, modern British food. "The emphasis is on simplicity," she says. "No heavy saucing or complicated garnishes. No towers." Until two years ago, diners in the evening had no choice about what to order: they had to have the "Sally Clarke menu". The chef-patron's certainty about what you should eat, heavily determined by what's in season, is deeply reassuring. Sally Clarke's customers are happy to deliver themselves into the hands of someone so regally confident. She is the culinary Queen of Kensington.

"Everybody told me it wouldn't work," she says. "You can't possibly dictate to people what they're going to eat. I thought, 'Why not? A housewife picks the choicest things in her garden. Why not me?'"

Today, she is a little more flexible. The Sally Clarke menu is still available – three courses for £39.50 – but diners have the option of ordering à la carte as well. "After 23 years, I felt I'd proved my point," she says.

When Clarke's first opened, it occupied the ground floor and basement of a terraced house, but in 1989 it expanded into the laundry next door and can now accommodate 90 covers in one sitting.

The atmosphere is posh without being ostentatious, a description that also applies to most of the customers. Clarke's belongs to the Kensington of JM Barrie rather than American investment bankers, though they have been known to darken its doors in the past. What's impressive about the restaurant is that it doesn't seem any less full in spite of the credit crunch – unlike Kensington Place, opposite. When I called to make a midweek lunchtime reservation, I was told the only available table was at 12.30pm.

During my visit, I opt for a salad of Aylesbury duck breast with pine nut and sultana cous cous, followed by chicken Kiev in a sauce of rosemary, fava beans and cream, while my companion has goujons of lemon sole and red mullet and, for his main course, thinly sliced beef salad with Italian peppers, black olives and cress. The highlight is the duck, but everything is light and summery, bursting with fresh, herby flavours. The only duff note is sounded by the lemon-curd and meringue "bombe" with pistachios and poached blueberries, which my companion pronounces slightly "sickly", but I have no complaints about my chocolate soufflé cake with raspberry coulis. I have been to this restaurant a dozen times and can confidently say I've never had a bad meal.

Like most successful restaurateurs, Clarke possesses an abundance of entrepreneurial flair and she has a small catering business as well as a shop next door. It resembles an upmarket French patisserie, with a combination of sweet and savoury treats, and is the perfect solution for maiden aunts hoping to entertain their nieces and nephews for tea. A 12-inch box of chocolate roulade with black and red currants costs £29.50, but will earn you the undying love of anyone under 10.

Clarke's isn't cheap. But if you have something to celebrate, I can't recommend it highly enough. And you might catch the eye of Britain's greatest living artist in the corner. A napkin doodle from him is probably worth more than one of Picasso's.

18/20

Scores: 1-9 stay home and cook, 10-11 needs help, 12 ok, 13 pleasant enough, 14 good, 15 very good, 16 capable of greatness, 17 special, can't wait to go back, 18 highly honourable, 19 unique and memorable, 20 as good as it gets

Clarke's, 122-124 Kensington Church Street, London W8, tel: 020 7221 9225. Lunch all week; dinner, Mon-Sat. About £50 per person, including wine and service

Second helpings: More long-term fixtures

The Cellar

24 East Green, Anstruther, Fife, tel: 01333 310 378

For superlative fish straight from the sea, nowhere comes close to Peter and Susan Jukes' venture of 25 years. The cave-like room is an unusual setting, too

Lino's

122 Market Street, Hoylake, Wirral, tel: 0151 632 1408

Established on the Wirral for more than 20 years, the Galantini family's comfortable Italian is a place where food is reliable and service is memorable

Le Champignon Sauvage

24-28 Suffolk Road, Cheltenham, tel: 01242 573 449

One of the UK's gastronomic gems. David Everitt-Mathias offers some intelligent and imaginative cuisine, underpinned by incomparable service (from wife Helen)