To dwell on the work of a chef can mean ignoring the obvious: the restaurant itself. The room must buzz. Food, to be enjoyed, has to be served on time and in good condition. Enter the restaurant manager and waiting staff. Many are efficient. Some managers, however, are a bit special. And this month, two of the best of the younger generation in London, Martin Saxon and Jill O'Sullivan, opened new restaurant doors.

So far, however, 'best' can only be applied to their floor shows. Neither has yet shown real staying power. For the last several years, Mr Saxon has seemed a bit of a Scarlet Pimpernel: we seek him here, we seek him there. He would open a restaurant, then make tracks. He was at the ill-fated Columbus in South Kensington, more recently in the lovely dining rooms of the Square in St James. I suspect - no, hope - it will be different with his latest restaurant, the Lexington. This bit of Soho needs a casual class act. And he certainly should stay at the Lexington. He owns it.

He had the wit to snap up the site of Sutherlands, which lurked behind smoked glass. Saxon has opened up the front, made it bright and welcoming. Out went the draped tables and finery. In came sleek banquettes and hardwood bistro tables. Down came the prices.

Like the room, the wine list is the soul of modernity: not too long, not too expensive and very alluring. I would like to spend time with its Italian, American, Australian and French bottles. We drank a honeyed but dry 1990 Jurancon Sec from Domaine Cauhape, in the somewhat obscure province of the Basque country.

The chef is Ian Loynes, formerly sous-chef at the Square. The menu is short and appetising. Everything sounds good. Most of it is, and what is not can easily be improved. The best food was excellent, such as a fricassee of lamb's sweetbreads and tongue.

Offal, if not a prime cut, is prime stuff, especially the tongue. It includes the leanest and most intensely flavoured meats. The tongue was cooked to absolute tenderness, served with mash in a finely textured sauce that was given a punch from what tasted like (I think) mint, thyme and sage.

Escabeche of mackerel was well handled, the skin seared before marinating. Served in an excessive pool of olive oil, it wanted only a dash of good sherry or balsamic vinegar. The parsnip soup was ace.

A dish called the Lexington Paysanne is the cousin of something done much better at the Square, a sort of puff pastry-based pizza. Here the star was smoked tomato, which had a good barbecue flavour.

The puddings need more work: the mousses were fatty and over-emulsified, and the pear tart tatin was a misbegotten clump of pie. But the coffee is excellent.

JILL O'SULLIVAN is the tall Irishwoman who left Launceston Place in west London last year to launch the tiny Italian restaurant, L'Accento, in Westbourne Grove. She tends to get things to customers almost before they know they want them. Before she moved on, her brothers built an ingenious platform from which she kept watch over L'Accento. The Italians who now run it must be crying into their beef braised in barolo that she left for Ransome's Dock, a riverside restaurant in Battersea.

One good reason for the move has been to help the chef and co- proprietor, Martin Lam, set up shop. He is a well-loved figure in the restaurant industry and has cooked for 10 years at the Soho restaurant L'Escargot. He is serious about good food. People who know him say he is obsessive about sourcing good produce and he pores over cook books; in short, he cares. His new menu is quietly British, even dutiful. His rabbit terrine is credited to Jane Grigson. Last week he employed smoked haddock, grouse and Scotch beef. Vegetables are autumnal and probably British. The French got a show with Brittany sardines, Italians with pasta and truffle oil, the Irish with smoked salmon and farmhouse cheese.

Best of a recent meal were excellent little mussels from Wales served a la creme. Smoked haddock, baby spinach and potato salad needed only a punchier dressing. Watercress soup was silky and soothing.

I was a bit baffled by the main courses. Chicken was sectioned, the skin seasoned, and cooked under the grill to suggest roasting. The flesh, while cooked, was slightly watery. It arrived on a bed of tagliatelle in an earthy mushroom sauce. Chicken bones and gristle tangled with the noodles.

A great heap of fish stew served with a mountain of dry couscous included all sorts of goodies: gurnard, squid, mussels and what tasted like monkfish. The seafood was perfect but the tomato sauce needed punch, some garlic and cayenne and black pepper. Little quails were wonderful, their skins seemed highly seasoned by some sort of marinade and cooked crisp by grilling. Around them were lightly cooked grapes. Why?

I prefer the grapes juiced and fermented at Ransome's Dock. The wines are exceptionally well chosen. There is much that is affordable and almost all is special. A 1990 pinot blanc d'Alsace from Hugel was so perfumed and elegant that it silenced us as we began to drink. At pounds 7.50 a half, or pounds 13 a bottle, it is curious that the wines of Alsace are not on more lists. The red, Nine Popes 1991 from the Barossa Valley, was huge and delicious. I am told it comes from the grenache grape, and is an Australian attempt at a Chateauneuf du Pape-style wine, hence the name.

As for the restaurant itself, it aims to be soothing. It feels rather like a Caribbean holiday home. The room is painted in tropical blues and greens, and all manner of prints and tiles have been hastily stuck on the walls. The Thames flows by river-facing windows. Ms O'Sullivan moves around the room briskly and gracefully. It is her job to settle this place in, to lend it warmth and tone.

The Lexington, 45 Lexington Street, London W1 (071-434 3401). Approx pounds 20- pounds 25 including wine, coffee, service and VAT. Vegetarian meals. Major credit cards except Diner's.

Ransome's Dock, 35-37 Parkgate Road, London SW11 (071-223 1611). Approx pounds 25- pounds 30 including wine, coffee, service and VAT. Vegetarian meals. Major credit cards except Diner's.

(Photograph omitted)