Gallery Mess, Saatchi Gallery, Duke of York's HQ, King's Road, London SW3

The only officers' mess I've ever seen is on screen: the one in Cairo in Lawrence of Arabia, into which Peter O'Toole walks wearing his battle-scarred Arab robes and supporting a knackered Arab boy with whom he's just, triumphantly, walked through the desert. I remember the British officers holding pink gins, radiating disapproval and telling off the adventurer ("Now look here, Lawrence ...") for going native, poncing about in a djellaba and ("Throw them out, somebody ...") bringing his frightful Ganymede chum into the mess with him. I don't remember seeing any food. And it would have smacked of pretension if T E Lawrence had, in such circumstances, asked for a lunch menu and ordered the venison carpaccio.

The Gallery Mess is a lot more welcoming. It's the new restaurant at the Saatchi Gallery, housed in the old Duke of York's officers' mess. Walking in from the King's Road, your spirits lift in the long front bar behind which a hundred bottles of Veuve Clicquot and a few score homemade loaves and bags of coffee adorn the shelves, their multiplicity making them shimmer like an Andy Warhol array of soup cans. You can eat in here, gazing out the window to the Gallery lawn, or stroll through into the more enclosed sections. It soon feels like you're in a gallery: exposed brickwork emerges from white-painted ceilings and arches, while neon installations add a touch of sophistication (though I suspect the neon red-headed woman on all fours, apparently emitting stars and moons from her bottom under the word "Forgiveness", might put some diners off their soup).

My date Madeleine and I sat in the main dining room, under scores of recessed lights. It's very stripped-down, with round white tables, simple green chairs, white gallery walls and artworks. If you've a few hundred quid to spare, you can buy the smaller pictures, eg of a dead sparrow and a mouse in a trap by Joss McKinley, though the head and shoulders of a man done in a beautiful mosaic will set you back £25,000.

Both the maître d' and our waiter said "Not a problem" so often, in answer to all menu decisions, wine choices, queries, comments and remarks, I thought it might be another clever installation – the phrase that, by repetition, becomes a problem in contradiction of the actual words – but decided no British artists could be so cunning.

The dinner menu is laughably small, reminding you that the Mess's main function is a café/bar for breakfast and lunchtime snacks. Its main courses hum with predictability (Cumberland sausage with lentils, chargrilled chicken breast, classic burger and caramelised onions) though its daily specials show a little more life. It's been reported that Nigella Lawson, wife of the gallery's eponymous owner, was so thrilled by the opening day's special menu, she ordered everything on it and demolished the lot. We did our best. Madeleine's prawn cocktail was served in a sundae glass: juicy prawns and "lepping-fresh" crayfish in "bloody mary" crème fraiche, so cold and fresh tasting, it gave us goosepimples. It was hard to detect much vodka or Worcestershire sauce in the dressing ("Just posh Thousand Island, isn't it?" said Madeleine), but it was delicious. In my English asparagus salad with organic egg, the tepid, soft-boiled egg was off-puttingly coated in slimy green watercress sauce, but the asparagus itself was unimprovably al dente, a real taste of summer.

After another fusillade of "not-a-problems", a problem appeared. My saddle of lamb was so undercooked it was practically rare, and I had to send it back. Rare beef is invariably delicious; rare lamb is invariably wobbly and sickly and hard to cut into. A second try was better, and I could appreciate the spiced red peppers which dotted the couscous and made war with the jasmine sultanas: an interesting, north-African take on an old English cut of meat.

Madeleine's spiced steamed salmon was perfectly cooked, invigorated by a slather of tomato chutney spread along the top like breakfast jam on toast and finished with a light curry broth. Salmon and curry combine in perfect Anglo-Indian harmony, but I wasn't crazy about the chutney. In dishes like this, two's company and the tomato was (so to speak) a gooseberry. We finished with a sensational knickerbocker glory served in a tall vase, with strawberry ice cream, berries and layers of crème brûlée; the only false note was an intrusive lump of yobbish peanut brittle.

The owners have put a lot of money, style and panache into Gallery Mess. Despite the limitations of the menu, the quality of cooking is much higher than you'd expect to find in a gallery restaurant. The place is a long, airy, white-walled, glass-fronted, coolly arrayed temple to both art and food, and when the sun's out in the King's Road, it will be packed. And if someone has a word with the waiters about not reciting clichés all evening, that would, for me, be Not a Problem.

Gallery Mess, Saatchi Gallery, Duke of York's HQ, King's Road, London SW3 (020-7730 8135)

Food
Ambience
Service

About £90 for three courses with wine

Tipping policy: "Service charge is 12.5 per cent discretionary, of which 100 per cent goes to the staff; all tips go to the staff"

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