Ashmolean Dining Room, Beaumont Street, Oxford

Lofty ambitions

This week we're floating high over the Oxford skyline, in a dazzling glass box of a restaurant on top of the remodelled Ashmolean Museum.

The room is packed, at 12.30 on a Friday lunchtime, with what appears to be a perfect cross-section of pleasant-looking people – imagine an entire Just a Minute studio audience infiltrated by a few architects in chunky specs. If the lunchers were an exhibit in one of the galleries below us, they'd be easy to label: "English middle classes; prosperous; early 21st century".

The view over the rooftops is predictably wonderful. Let's get the mandatory reference to dreaming spires out of the way; the place is surrounded by the bloody things. The old college friend I am lunching with could probably identify them, if we hadn't both gone to college several hundred miles to the north. And there's the unexpected plus of a view right into the bedroom windows of the Randolph Hotel; management must be placing an order for new net curtains even as we speak.

The excitement is palpable. Oxford has been pumped (to use a very non-Oxford word) about this £61m reinvention of a familiar friend, and the result is thrilling. Behind the museum's neo-classical façade, the architect Rick Mather has doubled the exhibition space, creating a modernist labyrinth of interconnecting galleries, vertiginous plate-glass walls and suspended walkways.

At the top of the building, the 90-cover restaurant has been magically raised on the roof; a glass-walled rectangle with light pouring in from all directions. Curvy Arne Jacobsen chairs and a couple of central canteen tables for communal dining give an informal, almost café-like feel, but the well-drilled waiting staff and ambitious menu mark this out as a restaurant with designs to become far more than an add-on to the museum's visitor experience.

The men responsible are Ben and Hugo Warner, who already run the Serpentine Bar and Kitchen and the V&A, as well as the Benugo group of cafés. Fittingly, in a museum whose new slogan is "Crossing Cultures, Crossing Time", they have put together a menu that manages to be both pan-European and winningly regional.

Italy is the prevailing influence, with a whiff of Middle Eastern promise. Our meal started with a silky, smoky babaganoush, to be scooped up with lavash, a thin wholemeal flatbread. Next we were introduced to the unknown pleasures of robiola and mojama – not the architects who failed to get the Ashmolean gig, but Italian soft cheese and salted, dried tuna respectively. The former came whipped with chives into a dip, with garlic-rubbed crostini, the latter in a zippy, well-balanced salad, with piquillo peppers, caper berries and a wobbly poached egg.

For those not wanting a blow-out, it would be possible to put together a fine meal out of these tapas-style plates, designed for sharing. But in the spirit of a museum whose decorous frontage conceals an unexpectedly cavernous interior, we moved on to substantial main courses from the selection of "large dishes", mainly priced from £14.50 to £17.50.

My friend's cassoulet was the proper job, its golden carapace of breadcrumbs giving way to a porky mulch harbouring Toulouse sausage and confited duck leg. My chargrilled sea bass was advertised as coming with gremolata, but arrived at the table nude; when I protested, it was removed and swiftly returned with its promised slathering of parsley and lemon zest, but with no explanation or apology. It was a nicely cooked piece of fish, though, the skin blistered from the grill, the flesh sweetened by herbs, and the accompanying boulangère potatoes were outstandingly good.

As my friend observed: "It all tastes home made, in the best possible sense." And that homely touch continued through a pudding menu which offers nursery classics like treacle sponge, or our own choice, a nicely unsweet baked custard tart, the pastry butter-rich, the custard velvety under its nap of nutmeg.

Our bill came to £40 a head before service, £19 of which went towards a carafe of Tinpot Hut Sauvignon Blanc. Which puts the Dining Room at the top end of the market in a city surprisingly short on good restaurants. They are already turning customers away at lunchtimes, when there's a no-bookings policy for parties smaller than five. But the space will really come into its own at night, with the skyline twinkling on one side, and the darkened galleries of the museum visible on the other.

So hats off to those clever Warner brothers, who clearly understand the theatre of eating out, and have created a restaurant which lives up to its spectacular setting. We've all grown up a bit since the days when a cultural institution could be reviled and lampooned for advertising itself as "an ace caff with quite a nice museum attached", as the V&A did in 1988. For which, let us give thanks, and congratulate the good people of Oxford on their ace new arrival.

Ashmolean Dining Room, Beaumont Street, Oxford (01865 553823)

Food 4/5

Ambience 3/5

Service 3/5

£20-£30 a head without wine

Tipping policy

"No service charge on tables of four adults or fewer – otherwise it's 10 per cent discretionary for five or more. All tips and service charge go to the staff"

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