Tony Cragg's work enhances the triple height staircase

The gallery, on Millbank in central London, has chosen a development that shows off the works of art it displays, rather than one with glamorous architecture.

"I have a preference for galleries which do not try to upstage the art," said architect John Miller. "For us the key thing has been light and space."

The new spaces have already received critical approval for their elegant integration of old and new.

Tate Britain's historical quirks - including World War II shrapnel damage to the exterior and air-raid signs in the basement - remain intact.

It is the traditional, watercolourist who struggles to make his way today

Prince Charles

A wall signed by leading UK figures in the arts, including Tracey Emin and Howard Hodgkin, is still there, but hidden behind the rebuilt walls of the Duveen galleries.

At the opening, Prince Charles said art should not be viewed as elitist and was highly relevant to modern life.

The prince has loaned a painting from his own collection - a portrait of Frederick, Prince of Wales - which normally hangs in his study.

The prince said traditional techniques were just as valid as newer, more experimental art and were deserving of a place in state school education.

The next challenge will be to strengthen the collections and to make them more accessible to encourage new audiences

Sir Nicholas Serota

He said: "Whereas 100 years ago, an installation artist may have received short shrift from the art colleges of the time, it is the traditional, watercolourist who struggles to make his way to day."

The new development has created four new galleries within the main building, and six new temporary exhibition spaces - the Linbury galleries - on the lower floor. Five existing galleries have also been refurbished.

The increased space will allow important works to be brought out of storage. Artists such as Bacon, Gilbert and George, Gainsborough, Blake and Turner will be given more space.

The National Lottery funded some �18.75m of the project through the Heritage Lottery Fund.

Manton entrance: Complete with bomb damage

Heritage fund chair Liz Forgan said the project was "particularly close" to the heart of her organisation.

"This project is what we're all about - conserving and displaying the treasures which Britain possesses in greater numbers, to better effect and accessible to more people," she said.

Tate Director, Sir Nicholas Serota, says that the new building is "only the beginning" of his plans for Tate Britain.

"The next challenge will be to strengthen the collections and to make them more accessible to encourage new audiences," he said.

Tate Britain is to lay out its collections in broadly chronological fashion, rather than in themed rooms as has become popular at Tate Modern.

But there will be temporary themed exhibitions drawing on the collections of Tate Britain and others.

The opening show is Exposed: The Victorian Nude, which draws together works by Rossetti, Alma-Tadema, Sargent and many others.