Marcus Wareing may be one of Britain's most gifted and garlanded chefs, but for his new venture, he hasn't traded on the pulling power of his own name. In the splendid dining room of his new restaurant at St Pancras Station, I overheard a woman ask, "Who is this Gilbert Scott bloke anyway?", clearly wondering why she'd never seen him on Great British Menu.

Fittingly, the man with his name over the door actually designed the door in question. Sir George Gilbert Scott was the architect of the Midland Grand Hotel, that masterpiece of Victorian Gothic which looms over the Euston Road – and now the Eurostar terminal – like a mad old uncle who won't accept that the days of Empire are over. Triumphantly restored to its former glory after decades of disuse, the newly reopened hotel is a thrilling place to visit, whatever you think of this gloomy, monumental style of architecture.

The Gilbert Scott sits in the heart of the building, in the same space as the hotel's original restaurant, and can be reached through a busy bar area, or through the cathedral-like hush of the hotel. David Collins's design for the curving, high-ceilinged room evokes a vintage, steam-age elegance, but despite the grandeur of its marbled pilasters, towering paintings and ornately corniced roof, it's still unmistakably a brasserie. Waiters bustle about in black braces, their ties tucked into crisp white shirts. It's like finding an offshoot of the Wolseley beamed down into the Victorian and Albert Museum.

Wareing was meeting and greeting when I visited for dinner a couple of nights after the celeb-packed gala opening. After escaping from years of quiet service within the Gordon Ramsay empire, he once again finds himself overshadowed by something much bigger, redder and showier than himself; this time it's a hotel. I passed him unnoticed, but hoped that later in the evening I'd get the chance to introduce him to my guests, a couple called the Murphys, the high bidders in The Independent's annual charity auction.

Mrs Murphy had warned me, via e-mail, to expect a well-padded couple from Devon in their mid-sixties, who'd be overnighting in a youth hostel so they could enjoy a "good vintage bottle of wine – or three". When they didn't show, I looked for them in the bar – and bumped into my friends Richard and Emma, just arriving, with inexplicably huge grins on their faces. They were, it turned out, "the Murphys". Tired of waiting for me to invite them out on a review, they'd taken matters into their own hands and placed the winning bid.

As befits a woman who has been hiding a dark secret from someone close to her for several months, Emma immediately identified the room as "very Brief Encounter"; there's a distinct touch of the station buffet about the red leatherette seating and punched bronze light fittings. Anyone planning an illicit assignation, though, would do well to request one of the roomier central tables – the banquettes around the edges offer a third-class lack of elbow room.

The menu is huge, some 15 starters and a similar number of main courses, and like the room, has a distinctly retro feel. Just as Heston Blumenthal has done at Dinner, Wareing and his protégé Chantelle Nicholson have taken inspiration from old cookery books to create their own thoroughly British version of brasserie cooking. Many dishes are unfamiliar – Harrogate loaf, The Queen's Potage and Tweed Kettle, for example (surely they made that last one up?) – and the list visits more obscure regional destinations than an old edition of Bradshaw's railway guide.

Happily, the intellectual promise of the menu is followed through on the plate. The dishes we tried may not have looked particularly pretty, but they were prepared with the finesse you'd expect from a team with its roots in fine dining. "This is what I dream of when I cook," breathed Emma as she cut into her baked onion, immaculately stuffed with a breadcrumby rubble. Mushrooms on sippets (toast, actually) were elevated from a breakfast dish by lozenges of bone marrow. Bacon olives – minced pork wrapped in bacon, served with an endive and shallot salad – sent Richard into a reverie. "It's comfort food," he sighed happily. "All the tastes of home and youth..."

The Gilbert Scott may be a brasserie, but the starter portions struck us as rather dainty. Not so the altogether heartier mains. Suffolk stew combined mutton meatballs with lentils, pearl barley and the occasional, surprising fishy gust of anchovy, into something that owed more to Scandinavia than to Suffolk. Dorset jugged steak – slow-braised featherblade which yielded to the fork like the filling of some celestial pie – came with sprightly pork dumplings and a sticky port reduction.

I encouraged Emma to order "soles in coffins" for the weirdness of its name; it turned out to be the straightest of our choices, a decorous piece of lemon sole in a Vermouth cream sauce, on a bed of puréed potato. She was more excited by the side dishes, particularly the pease pudding, split yellow peas cooked in ham stock to retain a nubbly, al dente texture. We also liked the sage and onion Paxo, a pimped-up version of the packet staple. "It's the 1950s gone delicious," as Richard said.

The use of nostalgic brand-name products continues with desserts, which include Turkish Delight cheesecake and orange marmalade Jaffa Cake. This last, a sticky sponge pudding wrapped in candied orange slices, came with Earl Grey ice-cream, a nice idea let down by the anonymity of the ice-cream. The partnership of Eccles cake with cheddar cheese ice-cream worked better. Still, we enjoyed both, and the other three desserts we tried – those Murphys do like a pud.

True to Mrs M's e-mail, we also made a crack at getting through the threatened three bottles. No vintages though – the wine list sticks to the middle range, though it roams across New and Old Worlds.

Our bill was unrepresentatively high, at over £100 a head, but this was a special occasion, and it would be possible to use the place more casually. The nostalgic glamour of the Gilbert Scott left us feeling as though, like Celia Johnson in Brief Encounter, we'd been a very long way away, back to a more elegant age. Only let's face it, the food back then would never have been this good.

The Gilbert Scott, St Pancras Renaissance Grand, Euston Road, London NW1 (020-7278 3888)

Food 4 stars
Ambience 5 stars
Service 5 stars

Around £40 a head before wine and service

Tipping policy: "Service charge is 12.5 per cent discretionary, of which 100 per cent goes to the staff; all tips go to the staff"