Emily Green suggests Beer and mussels at the brand new Belgo Centraal

popularising flemish phonetics and serving mussels by the ton might not be everyone's idea of a get-rich-quick scheme, but it seems to have worked for the French-Canadian entrepreneur Denis Blais and his Anglo-Belgian partner, Andr Plisnier. At least it hit paydirt three years ago when they opened Belgo, a Belgian-style theme restaurant in Chalk Farm, and it looks as if it will work again. Yesterday, a vast and cavernous new Belgo opened in Covent Garden.

To judge by its condition mid-day Wednesday, there is probably still some "snagging" in order. Hoardings were still up over the windows of what was originally a brewery and latterly a failing restaurant and subterranean lair of a legendary local landlord. Inside, the buzz was one of controlled panic.Waiters were reporting for fittings while only feet away builders were still fast at work, hammering, painting, even welding behind a shower of sparks. Tables were being laid at the same time doors were being hung. A suave-looking designer type was consulting over the installation of chic fittings in futuristic loos. When I arrived, the man overseeing the kegs of beer clattering down Shelton Street thought I was the new receptionist. It was tempting to play along: this new Belgo looks fun.

And it sounds funny. Its formal name is Belgo Centraal, ja, centraal, pronounced with a show- doctor- your-throat sound. Meanwhile, to avoid confusion, the original Belgo, opened in Chalk Farm in 1992, has been renamed Belgo Noord, pronounced like "floored". Such is the confidence that Centraal will succeed that the owners have already announced plans for a Belgo Zuid, presumably in south London - and Belgos all points of the compass, including Dublin and Edinburgh.

This plan would qualify as a threat were not Belgo, along with Aroma coffee shops, Pizza Express and Pret Manger, one of the better chains colonising our high streets. The expansive ambitions of Belgo's owners become clear when looking at their past: the Belgo was their fourth attempt at a chain prototype, done after they had worked together on the original Dme cafe, opened a tapas bar together and opened a licensed playpen called the DNA bar in the Trocadero, where most of the customers were underage, or simply acted that way.

Belgo outclassed these early efforts, no small thanks to the Belgian beers, of which there were 50, including rich trappist ales. Centraal will have 100, along with a beer shop, 16 genevers (gins) and two akvavits. There will be the mussels platters, served with chips and mayonnaise, at £7.95. For those immune to the charms of mussels done 16 different ways, there will also be soups, steaks, salads, cured herrings and chicken from a rotisserie. Formula food, yes, but cooked freshly and publicly: the entrance ramp overlooks the kitchen. Here we see the preparation of dishes with names the cooks themselves probably cannot pronounce, mash called stoemp and sandwiches called tartines.

Training at Disneyland would be a useful qualification to work the floor. Waiters are togged out in modern approximations of monk's habits. Other tricksy touches include racks of shot glasses, and the importation of specially blown brewer's glasses, some so unstable that they require wooden props. At first glance, this playful junk sits strangely with the basic fittings, laid in by the modernist architects Ron Arad and Alison Brooks.

Their choice of metal and ply seems like the stuff of butch utilitarianism, and there are commendable touches, such as the wire-cage lift, which permits wheelchair access. Yet, think about it, and the overall style is a fanciful mix of sci-fi film set and hi-tech bachelor's pad. Loos are artsy versions of Portakabins and the washbasin a big stainless thing, a design, according to Mr Blais, commonly found in American sports stadia. Use of causeways and refectory seating is meant to convey what Belgo's proprietors call their "transit concept". Roughly translated, this means that a good share of the restaurant will be seated on a no-bookings, first-come, first-serve basis. This supposes demand will be high. And yes, I expect it will.

Belgo Centraal, 50 Earlham Street, Covent Garden WC2 (0171-813 2233). Open daily 12noon-11.30pm, Sun to 10.30pm