GREAT COURT.

When the national library moved out of the British Museum many felt alarmed. In fact, the move has made possible rejuvenation of the Matron of Museum Street, which will make the much-loved building more welcoming.

Robert Smirke's British Museum, built neo-Greek between 1823 and 1852, was the first public museum in Europe. It is the second most popular attraction in Britain (after Blackpool Pleasure Beach) and has become the most visited museum of its kind in the world.

Smirke's original design was simple: a two-room deep front range behind the famous portico led to one-room deep ranges which enclosed a noble central courtyard. But as the collections and roles of the museum grew, the plan was radically altered -- most dramatically by Robert Smirke's brother Sydney who took over as architect and started to build the circular reading room in the Great Court only a couple of years after the main building was finished. Thrusting a circular peg into a rectangular hole left uneasy triangular spaces in the corners of the orthogonal space, but these were used by the staff (and worked quite well) for book storage.

Removal of the national library to new premises (AR June 1998), allowed the museum's whole strategy to be rethought. For a building that has sometimes to accommodate nearly as many visitors as Heathrow, the world's busiest airport, arrival and reception facilities were woefully inadequate. After an open selection process, Sir Norman Foster & Partners were appointed as consultant architects for reorganizing the museum and revitalizing the Great Court.

Their final proposal, which is now being built, was as seemingly simple as it was bold. A glass roof will link the rectangle to the circle: the Great Court will be re-evoked as a fine public space. All the corner bookstacks will be removed and the drum of the reading room will become a free-standing object. The Court will become part of the museum's arrival sequence which will become spacious enough to cater for the crowds. Circulation across the middle of the plan, previously blocked by the library, will be freed; long and tedious journeys round the perimeter will be obviated.

At a stroke, the place will be transformed. But there were great difficulties in achieving simplicity. For instance, the lightweight roof had to span from the rectangle to the circle with no intermediate supports; the circle was not exactly central within the rectangle. The structure, evolved with Buro Happold, is a triangulated toroid, designed to bear vertically on Robert Smirke's walls round the court, and its loads are taken by composite steel and concrete columns round Sydney's drum concealed behind new stone cladding. Climate control (also designed with Happolds) is equally ingenious, using a combination of natural and mechanical ventilation, radiant and convective cooling to achieve gallery conditions with minimal use of artificially generated energy.

New elements were tricky to design and build, but the old fabric had to be enhanced as well. Robert Smirke's Portland stone elevations and his four in antis Ionic porticos are being restored (north and south ones had been radically altered). Sydney's brick drum, which was never intended to be seen from the outside, is being given a Portland stone skin. The reading room is being restored to Sydney's colour scheme, and a new reference collection (given by Paul Hamlyn) is to be installed in its lower levels so that you will still be able to use desks frequented by Marx, Gandhi, Sun Yat Sen and Kipling.

To the north, two elliptical platforms are being created round the drum; these will provide space for shops, temporary exhibitions and a restaurant. Removal of the British Library has allowed large amounts of space in Robert Smirke's building to be released, particularly in the north range, and these will permit the return of the ethnography collections which have been outhoused in the Museum of Mankind for 30 years. An education centre will be created under the courtyard, and many other improvements are intended to enable the Matron of Museum Street to welcome twenty-first century visitors with the generosity she offered to their nineteenth-century predecessors.