Behind the revolving doors of The Northumberland on Northumberland Avenue, a pigeon’s swoop from the top of Nelson’s Column, hides a gem of a restaurant so dazzling that it will leave a permanent impression on your retina. And that’s just the upstairs bit.

Before our meal my colleague and I were shown around the vast subterranean banqueting rooms which are among the grandest period interiors remaining in London, with a capacity of up to 1000 lucky guests. All are owned by top-end catering doyen Charles Boyd, who welcomed us in person to his eponymous brasserie housed upstairs in the former Marble Hall, the centrepiece of the original 500-room Victorian hotel.

Like everything else we’ve seen here it is an impressive space restored to its early splendour, all pristine marble and high ceilings with low-hanging chandeliers, gently lighting the well-spaced arrangement of tables. And then there’s the focal point of the double-height bar space, complete with black granite bar and antique mirrors, and two original Victorian wine refrigerators still chilling bottles with large ice blocks in the central cavity.

It’s all a bit overwhelming by the time you’ve taken your seat, with an ominous feeling that things can only go downhill from here. For the record, Boyd’s is an all-day brasserie serving modern French and British cuisine, and promisingly the menu prices aren’t as lofty as the setting might suggest.

As feared though there is a slight downturn with the mains, which is all the more disappointing after two extremely satisfying starters of crab and lobster bisque, and chicken liver and foie gras paté served in a mini kilner with fig chutney. My colleague’s sea bass followed slightly limp and undercooked while my special of scallops with mashed potato and field mushrooms lacked anything of real bite or contrasting texture.

Redemption was relievedly secured however with two cracking desserts of caramelised banana waffles and a masterful apple tart of delicate puff pastry, served beneath a melting ball of homemade vanilla ice-cream. It was a timely and welcome fulfilment of the meal’s early promise, despite the mid-prandial blips and the waiting staff’s propensity for refilling your wine glass a bit too zealously.

On evidence, it was a little surprising that the place was so sparsely populated for a Friday evening, with not much local high-calibre competition to contend with. One could posit that there’s not so much footfall down that side of Northumberland Avenue as other streets in the Trafalgar Square area, or that the restaurant is tucked away a bit too secretly, with mainly hotel residents primed for its existence.

It really is somewhere though that any Londoners with a taste for history and grandeur will have their appetites sated on several fronts, and not least by the largely dependable menu. On aesthetic merit alone, not many venues in London or indeed the country come close to Charles Boyd’s ambitious restoration venture.

Boyd’s Bar & Brasserie, 8 Northumberland Ave, London WC2N 5BY. www.boydsbrasserie.co.uk