There are a couple of basic truths in the restaurant business; one is that a basement restaurant is harder to fill than one on ground level, another is that hotel restaurants are hard to fill with non-residents. Take a restaurant like Number Ten that has both of these characteristics, and you've got to try especially hard to make it work. The best weapon in a restaurateur's armoury is a good kitchen, which brings me to my next point. The best restaurants are those where the chef is not anonymous, they're places where the name of the person in the kitchen is heralded; where the chef de cuisine takes not just plaudits, but also responsibility.

You may have noticed that increasingly restaurants are informing you of who's doing the cooking. If you eat out even occasionally it's as well to take this information in - a good chef can transform a mediocre restaurant into a great one as easily as the loss of a good chef can change it for the worse. Number Ten has taken this idea of personalising their chef and taken it to it's logical conclusion - his name is on the sign outside. Kevin Arundel is his name, and before I go much further I'll tell you that he's a very fine chef.

There are times when doing this job feels less like work than others, and taking two charming sisters to lunch is one of those times. I had the good fortune to be lunching with Marian Guimond and her sister Susan Fagan just before they set off for their summer holidays. I arrived a little before them and had time to take in the room. Despite being basement, it's light and airy and big tables were set with starched napery, a restful ochre colours the walls which are hung with prints, and there's a handsome fireplace that takes centre stage. Large, comfortable upholstered chairs make it a comfortable place to sit, and while I was looking about I was guessing at what lunch might cost here. The dining room has the quiet, assured feel of a very professional place and I took a stab at about £20 or £25 for a set lunch. It was a pleasant surprise, then, when we were given the menus to find two courses for £14 or three for £17, plus a 10% service charge.

The wine list had a similar effect; I was expecting to find a heavily marked up list and I didn't. It's not overly long, about sixty wines in all including half-bottles, but it's very reasonably priced. A few examples; a Vernaccia di San Gimignano at £15.50, a Sancerre for £20 and a Gewurztraminer for £19.50. The majority of the list is French, including a few Bordeaux crus bourgeois in the £30 range, but there's enough to choose from should the New World be your preference, and there's a lot of good wines listed for under £20. For once I picked a French wine, a Pouilly Fume listed at £21.50, since that's normally closer to £30 than £20. It did prompt me to wonder once again why some restaurants think that a big mark-up is a good idea. In the short term you'll extract more money from your customers' wallets, but in the long term you simply make them cross and possibly drive them never to return.

The menu is more than interesting; it's a showcase. I won't list it in detail as I suspect it changes quite frequently, but between us we picked the salad of roast quail with spiced pear and seasonal leaves, the roasted pepper and tomato soup, and the gateau of crab and celeriac for starters. While we waited for these, a tray of breads came to us, all fresh and very good. The starters really lived up to the expectations that had been building up in me, and there was much approval from Marian and Susan as well. I felt myself smiling with that contentment that comes from knowing that you can relax, certain that your food is coming from the hands of a master - a feeling I get a lot more rarely than I'd like.

Main courses were equally impressive. Marian had picked the pan-seared escalope of cod with spinach leaves rouille and a saffron aioli, Susan had chosen the cannelloni of goats cheese, roast red peppers and puy lentils with a salsa verde, while I'd picked the oven-roasted rump of lamb with a ragout of root vegetables. Now these were excellent dishes, carefully and expertly prepared. The cod was perfectly cooked and the saffron aioli had a delicacy of flavour that perfectly complimented the fish. The goats cheese cannelloni, beautifully presented, had a well-balanced mix of flavours, further confirming the kitchen's expertise. My lamb was cooked perfectly pink and even the root vegetables, not normally a favourite of mine, tasted good to me.

If you can get to the end of your main courses without the tiniest of quibbles, then you know you've eaten unusually well. Couple that with attentive and professional service and you know you've found a good restaurant. Even though appetites had flagged I was determined to taste a dessert, although Marian and Susan were doubtful. The menu had six choices including cheese, but when I read the words 'warm croissant bread and butter pudding with caramelised banana and butterscotch sauce' I knew I'd found the perfect end to the meal. Although we only ordered one, they thoughtfully arrived with three plates and three spoons so we could all tuck in.

By the time we'd finished our desserts the other diners had long since left, so when we asked for coffee we were asked if we'd take it in the lounge upstairs, which is where we had it. It's not often I can really enthuse about the food in a restaurant, but Number Ten produces excellent food. For the moment, while lunch remains at this price, it's a gastronomic bargain that's hard to beat. The bill, with a second bottle of wine, came to £99 for the three of us.