As destination venues go, this one takes some beating. Spiritual centre, architectural masterpiece, famous tourist attraction. No pressure, then, on the catering company who, with zero previous experience of running a restaurant, have launched a smart dining venue in St Paul's Cathedral.

The new restaurant, open at lunchtimes only, is a showcase for our newly resurgent food culture, giving the thousands of visitors who throng the area's chain diners the chance to sample modern British cooking and English wines (no, stop, come back!) in a handsome, vaulted room below the cathedral.

The concept of Sunday lunch at St Paul's was shocking to my companion, who was raised in the self-denying Church of Scotland. "You mean they serve wine?" he thundered, possessed by the spirit of John Knox. "What next – will they be opening a lap-dancing club?" This is the modern church, old-timer; in my Father's house, there are many fine-dining options.

Tucked in a side room in the crypt, just off the café area, the restaurant is small and pleasingly plain. It's not a room for City boys out for a fat lunch; more somewhere a Barbara Pym character might have lunch with her favourite curate. The natural disadvantages of the space – soaringly high ceiling and single, barred window – have been cleverly overcome with a split-level design, and there's a simple, almost Scandinavian aesthetic to the white-washed walls, sage woodwork and pale bentwood chairs. The only touch of luxury comes with the high quality of the accessories; heavy linen napkins, age-burnished silverware and massive slate placemats which would come in useful should any further Commandments be handed down.

We had a good chance to admire the décor during the five minutes we were left to hover uncertainly in the middle of the near-empty room, ignored by the sole waiter who was attending to one of the two occupied tables. Eventually we gave up and seated ourselves. The waiter offered no apology when he finally found time for us. Then we were moved to another table. We'd arrived in a state of calm and wonder, after a tour of the Cathedral. Now we were in a rage.

This wasn't helped by the absurdity of the menu listing prices in British pounds – as in "Organic bread and Jersey butter – 2 British Pounds". Yes, that's right, £2.50 for bread and butter. For that price, you'd expect a few fishes to be thrown in. Still, the bread was springy and fresh. And the short menu is full of lovely stuff, offering a round-Britain food tour, starting with an apéritif described as "Britain in a glass" – sparkling wine from Carter's in Essex, sweetened with rhubarb and apple juice to make a kind of home counties Kir Royal.

We skipped starters in favour of a shared jar of radishes with home-made salad cream, ie mayonnaise. The menu, in its mania for Britishness, likes to Anglicise wherever possible. So the "new bridge" chips which came with the beef fillet tail weren't thin and wobbly, in tribute to the area's most recent tourist attraction, but classic Pont Neuf potatoes, literally translated. The meat was tender and well rested, cooked to fall somewhere between steak and Sunday roast, and served with a light horseradish cream.

Both fish dishes we tried scored full marks for imagination and execution. Pollock, usually encountered only as a cod substitute in fish and chips, was here roasted in a spiced cep crust, and served with blanched samphire and cucumber. Even better was seared sea trout, its skin crisp and its salty orange flesh sympathetically partnered with a pale, frugal salad of shaved fennel, shallot and yellow beans, dressed with verjuice.

After a run of dessert menus featuring the same dreary options it was refreshing to encounter something a bit different here, including a "sandwich" of dense, dark gingerbread around honey ice-cream, from the owners' own hives in Regent's Park. A lemon verbena pie – less shrill than the classic lemon tart – had apparently been baked with the filling in, leaving the pastry heavy, but a roulade version of Eton Mess was the perfect light summer dessert.

The fixed price structure of the menu – £16 for two courses, £20 for three – means there aren't any nasty surprises when the bill arrives, and unusually, for a London restaurant, a service charge isn't automatically added. Despite our shabby reception, and the hour-long wait for food, we still obeyed the unofficial 11th commandment of the British: thou shalt feel obliged to tip 12.5 per cent, even when the service hasn't really been very good.

If they can sort out the front of house problem, this will be an attractive addition to the City dining scene. Until then, to echo the verdict of congregations down the ages, great church, shame about the service.

The Restaurant at St Paul's, St Paul's Cathedral, London EC4 (020-7248 2469)

Food 4 stars
Ambience 3 stars
Service 2 stars

Open for lunch only. Two courses £16; three courses £20

Tipping policy: "No service charge. All tips go to the waiters"

Side Orders: Culture vultures

National Dining Rooms

Oliver Peyton's organic food includes a Bickleigh White Park rib-eye steak with baby vegetables; great views over Trafalgar Square.

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The Fruitmarket Café

Edinburgh's funkiest modern art gallery has an eclectic café to match: try the local Scottish fish platter (£7.95).

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Tate Liverpool Café

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