Museums: Bridging a gap in London's history: Michael Leapman visits the exhibition at Tower Bridge that marks its centenary in 1994

TOWER BRIDGE in London prides itself on being possibly the only bridge in the world to house an exhibition. It is not difficult to work out why.

Bridges, even bridges that play clever tricks, are largely functional. They are of interest chiefly to the kind of enthusiasts who attend steam rallies, besotted by the romance of iron, pistons and coal-fired boilers.

All the same, Tower Bridge is special. As much a symbol of London as Big Ben and red double-decker buses, it has been attracting around half a million visitors a year since it was first opened as a tourist attraction in 1982.

It hopes to lure rather more with its pounds 3.75m refurbishment, involving new hi-tech animated displays which were unveiled last month in time for next year's centenary of its construction. With 2.3 million people a year visiting the Tower of London alongside it, the market is clearly there.

The bridge boasts two main attractions. There are the enormous Victorian engines that were used to lift the two halves of the roadway when it opened for ships: it is now electrically operated but the sleek old machinery is still in place. Then there are the high walkways linking the two towers, offering marvellous views up and down the River Thames.

Until now, these were complemented only by a rather earnest exhibition explaining the history of the bridge construction in diagrams, models and text. This has been replaced by 'The Celebration Story', a lively exhibit using the most modern animation and audio techniques.

Visitors are taken up in a lift and directed to the first gallery, where a talking and moving model of a construction worker begins to explain the history of the bridge, assisted by film clips and holograms.

The human models are animatronics and are very impressive. Their eyes swivel and blink, their fingers tap on the table in front of them and it is easy to mistake them for real people. Several appear throughout the 75-minute tour, either as actual characters involved in the tale, or as figures meant to represent the humble toilers.

There is nothing wrong with how they look: the problems start, however, with what they say. It is always hard for the creators of this kind of display to know just at what level to pitch the script. The trap - and I am afraid Tower Bridge falls headlong into it - is to adopt the folksy and jokey 'believe it or not' tone assumed to grab the attention of both young and old visitors.

An attempt is made to inject drama by playing up the debates about whether another bridge in London was really needed. The problem is that the characters involved - shipowners worried about obstructing access to the Pool of London; engineers submitting rival designs - are not interesting enough to make it work, even when voiced over by Timothy West. There is a great deal of chirpy ho-ho-hoing in broad regional accents, for many of the workers came from Tyneside.

Any trouble overseas visitors may have in deciphering them is alleviated by simultaneous translation equipment. A stoker nods off beside his coals and two men tease each other over which of them should be explaining about the bascules - the counterweights that allow the road sections to pivot upwards. As in bad melodrama, the overacting only serves to underline the thinness of the plot. However amazing an engineering achievement the bridge was a century ago, it is primitive stuff by today's standards.

The addition of an education centre, with 'a resource pack closely linked to the national curriculum', suggests that children are the main target for the exhibition. Certainly they will get the most out of standing in a scaled-down model of a bascule chamber, in apparent danger of being crushed as the bridge swings.

They may also enjoy the climax of the tour, a diorama of the 1894 royal opening, staged in a mock Edwardian theatre complete with an animatronic, moustachioed master of ceremonies.

The high point, in all senses, remains the views from the walkways. These will be even better appreciated once they get their full complement of 12 interactive video consoles, identifying the riverside buildings and letting you choose from a range of information about them. This is modern technology used sensibly to illuminate real history, rather than pastiche.

Tower Bridge is open every day from 10am to 5.15pm until the end of October, and from 10am to 4pm from November to March. Admission is pounds 3.60 for adults, pounds 2.50 for children and pensioners. Information on 071-378 1928.

(Photograph omitted)