What makes a restaurant wonderful? Certainly not clever marketing, nor the latest line in fixtures and fittings. Even first-class food and drink are not enough: the finest of victuals are wasted in inhospitable surroundings. The answer, which escapes too many caterers, is almost painfully obvious: a restaurant is only as wonderful as the people who run it.

By way of example, I offer the very wonderful Seafood Restaurant in Padstow, north Cornwall. The owners, Rick and Jill Stein, run the place themselves (and have done for nearly 20 years). Their staff have the relaxed confidence of family, which some of them are (Mrs Stein's father plays piano there on Saturday nights, and her sister helps to run the dining-room). Mr Stein is chef-patron, though this title fails somehow to conjure his good nature.

It helps, of course, that Mr Stein is the best fish cook in the country, author of the award-winning English Seafood Cookery (Penguin, pounds 8.99). It helps even more that he and his wife create restaurants of such casual elegance that they feel special but encourage fun. An atmosphere of easy, mildly pixilated charm prevails, not only in the Seafood Restaurant, but also, now, in its new satellite hotel, St Petroc's. It is here, within stumbling distance of the harbour, that a fortnight ago the Steins opened a new dining-room.

St Petroc is the patron saint of Padstow. The building named after him is a 16th-century house, the fifth oldest in the town. Like its parent restaurant, the hotel is decked out with confident and simple good taste: hardwood floors, white walls, bright, modern canvases. However, it is the details that really tell: table-cloths are paper, so mussels in sauce can be eaten with gusto and no worries about stained linen; fingerbowls are automatically laid out; napkins are cotton prints whose bright colours sing. The crockery also merits mention. Soups are served in generous china tureens; main courses on big, white, handsome plates. Smaller plates might have a simply patterned rim, eliminating any perceived need for twee garnishes.

At breakfast, honey accompanying fresh tangy yoghurt will be set out with proper wooden serving twirls - far better than spoons. This may seem an eccentric tool in a modern restaurant, but Mrs Stein is a bit of a genius at eschewing pompous clutter while retaining civilised implements.

Paul Hearn, the chef of St Petroc's, is a graduate of the Steins' kitchen down the road. He will need more time to refine and correct his food. No matter. The blueprint is there, drawn up, I suspect, by Mr Stein, and a jolly sensible one it is. It does not attempt to ape the food of the Seafood Restaurant. It is cheaper, simpler, and rooted in the staples of French bistro cooking: steak and chips, simply-done fish, mussels, game salads. Best of all, the menu is short and changes daily. There are three starters, three main courses, three desserts.

I ate three consecutive meals there and would gladly have stopped for a fourth and fifth. Unsurprisingly, moules mariniere were excellent. Better yet were mussels in a saffron sauce built on the cooking liquor, with melting leeks, a touch of cream, generous amounts of saffron and some ingenious and subtle background spicing (star anise? curry?). I tried two soups and each was astonishingly good: watercress and potato, in which the cress was there for flavour, not just colour, and vegetable, which came with chunks of strong, salty duck.

Hot game salads, so beloved of the French, are rare in England. St Petroc's had a wonderful version in the form of sliced smoked duck served on wilted dandelion leaves. The dressing was a vinaigrette made with what tasted like a French olive oil, its floral scent set off by the heat.

Only one starter needed a rethink. The Steins are new at curing their own beef in wine then air-drying it to make the Italian bresaola. The cut of meat seemed dinky and wrong, the texture too tough. Small slices were served with slightly tired rocket, and olive oil that had been over-generously blended with truffle oil. It was not a bad dish, simply a ham-fisted one.

Main courses had us back on track with astonishingly good grub. Tywardreath sausages were spicy, meaty, and perfectly cooked, then served with mash spiked with spring onion and good gravy. Baked cod came lightly (and perfectly) cooked with an onion confit, which, again, was forcefully and beautifully spiced with bay leaf, loads of pickled lemon, garlic and so on. There was a lot of it, possibly too much, but it was delicious.

It was a delight to see petit sale with lentils listed as a main course for Sunday lunch. 'It means little salted bits of pork, basically,' Mr Stein explained. Our bits included a pink sausage - sour in the Toulouse style - and slices of poached pork served with a sea of Puy lentils, with a beautifully tempered mustard as a condiment.

This is boldly plain, honest food; it is also unforgiving. It is too naked to disguise flaws, and just now, to my taste, the dish has several. There were too many lentils, which were too firm to serve as foil for the meat and too violently flavoured with thyme. A melting stew of plain lentils cooked with pork knuckle and a dice of sweet carrots and onions would have been better.

Puddings are styled strictly for the English table. Playfully gooey and judiciously sweetened meringues are served with clotted cream. The combination is superb. Stewed dried fruits, including apricot, fig, and intensely flavoured muscat raisins, are served with cardamom ice-cream. This is a near-perfect dish, topped for some reason with unseasonal strawberries and halved fresh grapes.

The wine list at the Seafood Restaurant is long, sophisticated and really good; at the little hotel it is short, sophisticated and really good. House whites include an austere sauvignon blanc and a flowery new-wave number from Gascony. The Chablis Laroche is lively and fresh on the tongue, the way the French and Italians like their wine. The wonderful surprise is that, while it is utterly delicious, it is only pounds 15.50 a bottle.

The Steins seem to attract marvellous staff. At the hotel they may still be learning the ropes, but their work has a swinging naturalness that sets guests instantly at ease. It is difficult to tell who is in charge. My guess is that it is the hospitable and charming Australian woman who listens to Neil Young tapes in the bar and makes nine-year-old guests happy with an exotic drink called a Fire Engine: a mixture of lemonade and grenadine.

St Petroc's, 4 New Street, Padstow, north Cornwall (0841 532700). Set three-course lunch and dinner pounds 13.50, approx pounds 20-pounds 30 inc wine, coffee, service etc. B & B for two, pounds 50-pounds 75. Seafood Restaurant, Riverside, Padstow (0841 532485). Set three-course lunch pounds 20.25, dinner pounds 27.85, pounds 35-pounds 40 all in. B & B for two pounds 55-pounds 106. Both places accept Visa, Access, Amex.

(Photograph omitted)