Terry Grimley takes a look at Coventry's Belgrade Theatre, which has had a #14million makeover.

When the Belgrade closed its doors to the public in February 2005, it was just one theatre: now it's reopening as two.

The country's first new theatre of the post-Second World War War era, originally opened in 1958, has added a new flexible 300-seat venue which will play a central role in artistic director Hamish Glen's strategy to re-establish the Belgrade as one of British theatre's creative hotspots.

An ambitious opening season has a distinctive European flavour with productions of Brecht, Bruckner, Horvath and Schiller, with Sir Trevor Nunn returning to the theatre that launched his career to direct an adaptation of Ingmar Bergman's Scenes from a Marriage. It's a step-change from the populist policy long associated with the Belgrade (not that more popular programming has by any means been excluded) which has grabbed attention far beyond the city's boundaries.

How the Coventry public responds to the new Belgrade remains to be seen, but what is already clear is that architects Stanton Williams have provided an inspiring new environment which declares that the theatre means business.

A new extension, which houses a new bar and box office as well as the second theatre (to be known as B2), has been seamlessly grafted on to the listed 1950s building.

Approaching from what I've always thought of as the front of the building - but which, confusingly, has now come to be regarded as the back - on Corporation Street/Belgrade Square, the cafe and foyer are much as before except that they have been cleared of clutter and redecorated in a cool grey and white colour scheme. The new furniture is subtly reminiscent of 1950s style, and the cool minimalism is a hallmark of Stanton Williams work, familiar from previous projects like Birmingham's Gas Hall and Compton Verney.

From outside it's easier now to spot the stylistic resemblance of the cleaned-up facade, which is still awaiting some restoration of perished concert with material retrieved from the adjacent, just-demolished Lunn-Poly building, to the Royal Festival Hall.

Martin Froy's original mosaic murals on the foyer walls, long covered up, have now been revealed and restored with the aid of the artist himself, who returned to the theatre for the first time after nearly half a century.

It's as you approach what used to be the back exit that you really enter a new era. Instead of stepping through a narrow door into a back yard with bins and parked cars, the foyer opens out into a new airy space with the box office on one side and a bar on the other, both on a generous scale. As well as the entrance to B2 there are also lifts here connecting with all floors, making the building fully accessible for the first time.

Beyond, a large window offers a view of a remodelled multi-storey car park with an exceptionally well-designed access tower. However this view will disappear over the next two years as the Belgrade Plaza development, which will include a range of bars and restaurants as well as two hotels and a casino to complement the theatre, goes up.

It will incorporate a pedestrian link between the theatre and the car park, which is staffed round the clock and has already won awards for its design. The fact that most evening visitors will arrive here by car explains why this previously uninspiring approach to the theatre is now regarded as its front door.

At first sight B2, which has a part-translucent fly tower which will serve as a beacon when illuminated at night, looks surprisingly small for a theatre with a nominal capacity of 300. Actually that will be a maximum, dependent on the format chosen for individual shows.

With seats on three levels it looks something like the RSC's Swan but translated from wood into a steely industrial look arguably more in keeping with Coventry. The balconies have a particularly tough, cheese-grater look. With much of the seating still to be installed this week, the set for the first production, Bruckner's Pains of Youth, was already being built onstage. Essentially a large box on a hydraulic lift, it looks remarkable.

The balcony overlooking the foyer extension has an elaborate mural in cast glass by Birmingham artist Lenora Minto commemorating the many public bodies, private organisations and individuals, including some theatre celebrities, who have contributed to the theatre's renaissance. Private fundraising for the scheme proved a great success and seems to have established a new partnership with local business which will continue to pay dividends when the theatre is up and running.

The 900-seat main auditorium has had new air-conditioning installed but has otherwise remained largely untouched, having been reseated not many years ago.

However, a makeover of the the first floor restaurant is just being finished off and the second floor, featuring a permanent exhibition on the history of performing arts in Coventry, is still to come.

Overall, it feels as though the new Belgrade has traded its former small-town cosiness for something altogether more sophisticated and businesslike. If London critics used to the National Theatre add it to their itinerary they shouldn't feel they've come to the provinces.

What's more to the point, though, is for West Midlands audiences to take it to their heart.

 The Belgrade Theatre officially reopens tonight with a Gala Evening featuring Humphrey Lyttelton and His Band.

The opening productions are Mr Puntila and His Man, Matti (Main house from September 22) and Pains of Youth (B2 from Sep 29). Box office: 024 7655 3055, More information at www.belgrade.co.uk