Quirinale, 1 Great Peter Street, London SW1

In a Westminster basement that once housed a club of dubious repute, Quirinale is cleaning up on MPs' expenses

If MPs really are being forced to "live on rations", as Alan Duncan claimed, that's bad news for the belt of fancy restaurants that encircles the Palace of Westminster. The Cinnamon Club may have to become the Cinnamon Brasserie. Wiltons may have to dispense with its division bell. When David Cameron starts slashing salaries and clamping down on expenses, MPs might not even venture beyond the House of Commons canteen for fear of being spotted eating a crème brûlée by one of the Tory whips. There will be no more Billy Bunters at Greyfriars next year.

One of the restaurants that doesn't deserve to suffer is Quirinale, an upmarket Italian on Great Peter Street. Consistently voted by Harden's and Zagat as one of the top three Italians in London, Quirinale is smart without being grand, the sort of place where you can pop in at lunch time for a plate of pasta and a glass of prosecco, or celebrate your birthday in the evening with a five-course tasting menu accompanied by a flight of wines.

Quirinale was opened in 2002 by Nadine Gourgey. A lawyer with a lifelong love of food, Gourgey decided that the House of Commons could do with a decent Italian less than two minutes' walk away and recruited Stefano Savio as head chef. "Stefano is from Brescia in northern Italy, but the menu isn't regionally specific," she says. "He uses ingredients from Sardinia and Sicily, as well as his hometown. I would describe it as modern Italian."

I first discovered Quirinale in 2006 when it was rumoured to be the unofficial Westminster headquarters of the Cameroons, but I had only ever been for lunch until last week. I decided that to truly put the kitchen through its paces I'd need to sample the full tasting menu over the course of an evening. To make things tougher, I asked if the restaurant could match my menu, dish for dish, with a vegetarian equivalent for my wife. Even though that's not one of its standard options, they said they'd see what they could do.

Quirinale is located in a basement in what used to be a fairly sleazy gentlemen's club, but the designer David Collins has created a light, airy space. There is a large skylight at the front, running the length of the restaurant, so you never get the feeling you're underground. The walls are pale green and the floor a stained white oak, creating a summery feel, even in winter.

I start with a timbale of crab with broccoli and crushed olives, while Caroline has a rocket salad. Both are nice and light – a good opener to a five-course meal. The next course is meat-free, so we both have the same thing: casoncelli stuffed with fontina cheese and liberally sprinkled with shavings of black summer truffle. This isn't my favourite dish, not least because it clearly derives its flavour from truffle oil rather than the real McCoy – and the combination of thick pasta, even thicker cheese and truffle oil is a bit overwhelming.

The next course is better – a fillet of Scottish beef on a bed of wild mushrooms, but my poor wife is given what looks like a suet pudding with an egg baked in the middle, doused in truffle oil. To drench one dish in truffle oil may be regarded as a misfortune, but to drench two...

After a pretty impressive cheese course, we are presented with a citrus fruit salad accompanied by a Campari sorbet that we both like. It goes particularly well with the 2005 Capitelli it is served with – Italy's leading dessert wine.

Oddly enough, by far the best part of the meal is the amuse-bouche, a little choux bun flavoured with spinach and ricotta, split in half and spread with what tastes like a chorizo paste. The staff momentarily forget my wife is a vegetarian and give us two each, but I have no trouble devouring all four. After such a spectacular start, the rest of the meal could not help but be slightly disappointing.

All in all, a pretty good experience – though better for me than Caroline. One of the three best Italians in London? Possibly. The best Italian in the Westminster Village? Definitely. And according to Nadine Gourgey, the clampdown on MPs' expenses hasn't hurt Quirinale yet. "To be honest, MPs are often taken here by journalists," she said. "And their expense accounts seem to be as fat as ever."

15/20

Scores: 1-9 stay home and cook, 10-11 needs help, 12 ok, 13 pleasant enough, 14 good, 15 very good,16 capable of greatness, 17 special, can't wait to go back, 18 highly honourable, 19 unique and memorable, 20 as good as it gets

Quirinale, 1 Great Peter Street, London SW1, tel: 020 7222 7080. Lunch and dinner weekdays; about £140 for two, including wine and service

Second helpings: Westminster worthies

Atrium

4 Millbank, London SW1, tel: 020 7233 0032

A spacious dining-room off the atrium of Parliament's media centre, its perennially lacklustre standards have, of late, been on the up

Cinnamon Club

30-32 Great Smith Street, London SW1, tel: 020 7222 2555

Westminster's old library is home to London's grandest nouvelle Indian and its unpretentious take on traditional dishes

Shepherd's Restaurant

Marsham Street, London SW1, tel: 020 7834 9552

The whole is greater than the sum of the parts at this club-like Westminster stalwart with traditional British values

Extracted from 'Harden's London Restaurants 2010'. IoS readers can buy a copy for £9.99 post-free (rrp £11.99). Send name, address and cheque to Harden's, 14 Buckingham Street, London WCN 6DF. Delivery within 14 days