Ivy Market Grill, restaurant review: 'I came to boo, but by the end of lunch, I'm ready to cheer'

1, Henrietta Street, Covent Garden, London WC2 (020-3301 0200)

The masculine dining room references the original Ivy, rather than slavishly imitating it (Paul Winch-Furness)

It's panto season again, and the stage is set for the traditional themed review. This year's production has a nostalgic market setting – a cobblestoned corner of Covent Garden piazza in olde London Town. It has an all-star cast – The Ivy Market Grill is an offshoot of possibly the most famous restaurant in Britain. And it has a baddie, in the form of Richard Caring, the Baron NotVeryHardup of the piece.

It's been nearly 10 years since (fashion) Baron Caring bought the Caprice Holdings group of restaurants, which then included The Ivy, Le Caprice and J Sheekey. It was the first acquisition in what's become an enormous portfolio of restaurants, members' clubs and chains. Nothing villainous about investing so heavily in the industry, of course, even if some of the group's more recent launches, such as Grillshack and Jackson + Rye, are just canny syntheses of other people's ideas.

But it's what's happened to The Ivy, the jewel in Caring's crown, that makes the restaurant-watchers in the gallery fearful. By opening a swish members' club directly above his theatreland favourite, Caring disastrously split the traditional Ivy crowd. The pleasure of the place used to be the chance it gave for civilians to mix with celebs. From Cilla and Dale to Jack Nicholson and Michael Caine, there was always someone famous to gawp at.

Now the famous are mostly upstairs in the Ivy Club (or at the Chiltern Firehouse), gawping at each other, and whoever else has a grand a year for membership. So having already extended the Ivy brand, Caring's decision to risk further dilution by launching a 'little sister' brasserie, just as the original closes for refurbishment, seems risky.

On first impressions, the new place, which occupies a roomy two-floor space overlooking the Actors' Church and the piazza, feels a lot more accessible than the mother ship. No top-hatted doorman here; walk-ups are encouraged to stroll in, past pavement tables which will be fought over in warmer months,

The low-slung, masculine dining room, dominated by a steel and pewter bar, references the original Ivy, rather than slavishly imitating it. Martin Brudnizki Studios, also responsible for the Ivy Club, are past masters at creating the illusion that new restaurants have been around for ever. The look here is mid-century Manhattan grillroom, dark, woody and leathery, and it works pretty well, despite the tell-tale whiff of fresh paint.

There's a prime row of slinky curved banquettes up one side, clearly the best tables. And then there's the room we're put in at the back, a dull, viewless dead zone which feels more like a branch of Café Rouge than The Ivy.

Like the design, the menu is inspired by, rather than copying, the original. It's an all-day, all-meals, all-occasions offer, starting with breakfast from 7am, and running through to the small hours. The choice is bewildering, taking in trad grills, seafood and snackier dishes – my eye is drawn by the truffled chicken sandwich on toasted brioche.

Some dishes are inspired by Ivy classics, and it's to these that we gravitate. Duck salad, the meat roasted Peking-style and shredded, comes with bean sprouts and pomegranate seeds, like the original, but it seems more substantial, and it's certainly prettier, heaped on translucent slices of black radish.

Prawn cocktail Marie Rose is properly served in a silver coupe with a muslin-wrapped lemon, and absolutely packed with prawns. There's no sense of corners being cut, or margins worked. Hang on, this wasn't in the script.

Main courses are even better. Lemon sole, golden under a mess of capers, lifts easily from the bone, and the fat, airy beef dripping chips are, to quote a departed Ivy regular, historic. Shepherd's pie made with slow-braised lamb shoulder and mash gilded with Keen's Cheddar, is better than I remember from The Ivy (and £5 cheaper); no wonder it's already the Grill's bestselling dish.

There's real finesse in a frozen milk chocolate parfait, proving the kitchen, under Sean Burbidge, the former head chef of Gordon Ramsay's Petrus, has skills well beyond the posh comfort food we've had so far. Even in Siberia, the service is first-rate, from aproned waiters who are clearly pros. I may have come to boo, but by the end of lunch, I'm ready to cheer; the Market Grill isn't just an Ivy diffusion line, it's a really good restaurant in its own right.

It may not have the A-list credentials of The Ivy, or the swagger of nearby Balthazar, but Caring has clearly invested to make it an A-team operation. And the Ivy crowd seems to be drifting across; we spotted a big West End producer among the early adopters, lunching with a casting director. If they're hoping to cast a villain in their next production, they are going to have to keep on looking.

Food ****
Ambience ***
Service ****

1, Henrietta Street, Covent Garden, London WC2 (020-3301 0200). Around £35 for three courses before wine and service. Pre-theatre menu £21 for three courses