The water coursing under the magnificent bridges has been dyed grey-brown to match the natural colour of the Thames.The models begin with Old London Bridge (the one that was always falling down) as it was in 1600, when it was decorated by the decapitated heads of traitors (a German visitor counted more than 30 in 1598) and continue through examples of the most famous (Rialto, Ponte Vecchio, Poulteney) and others that remained on architects’ drawing-boards. Coates has arranged 21 spectacular, purpose-built wooden models of inhabited bridges (made by Andrew Ingham & Associates) across a miniature river that snakes its way through the RA’s principal galleries. Peter Murray and Mary Anne Stevens, curators of the exhibition, appear to have successfully bridged the gap between the popular touch and scholarship.Nigel Coates, of Branson Coates Architecture, has designed the show, and it it promises to be quite breathtaking. Jean Dethier of the Pompidou Centre planned a exhibition of paintings depicting inhabited bridges through history. Because the Pompidou Centre will be closed for major repairs and renovation until the turn of the century, he brought the idea to London, where the Royal Academy has transformed it into a show that combines contemporary wizardry and a sense of occasion, drawing on years of detailed research by Jean Dethier.

Do we need a passport? Here be monsters.Given our fascination and even love of bridges, the Royal Academy of Arts can only succeed with Living Bridges, an exciting exhibition of that most intriguing of all river crossings, the inhabited bridge – like old London Bridge, Rialto Bridge, Venice, Ponte Vecchio, Florence, Pulteney Bridge, Bath – a feat of engineering that we can live, work and shop on as well as cross.Living Bridges began life in Paris as an over-the-shoulder look at the inhabited bridge in history. Which north Londoner can cross Tower Bridge, with that thrilling, shifting inch-gap in the middle through which the grey-brown tidal waters of the Thames can be seen churning, without a feeling of trepidation: at the end of the bridge is “sarf” London. Only the dullest human being remains unmoved or unexcited by bridges And each crossing remains an adventure. And, no matter how cloying the saccharine falsetto of Art Garfunkel singing “Like a Bridge Over Troubled Water, I Will Lay Me Down”, we cannot help but understand the sentiment.
We are fond of bridges, and appear to accept them for what they are, whether they are garbed in Neo-Gothic fantasy dress, like London’s Tower Bridge, or express the latest developments in structural engineering. New Yorkers speak of suburbanites who invade Manhattan on weekends as “bridge and tunnel” folk, because it is by these means that they invade the citadel of skyscrapers and chic shopping.

We talk of building bridges with other people, countries and organisations. Bridges are, of course, far more than a matter-of-fact way of crossing physical voids; they are the stuff of dreams and the imagination They are highly symbolic. We built them across streams with sticks as children; we sang “London Bridge is falling down” – although whenever I crossed it on a red double- decker, it looked sooty but perfectly sound. What if? What if there were a bridge that would let us cross this valley or that river at exactly the point we would like it to? We can all imagine new bridges, and many of us will have our own ideas as to where they should spring from and where they should touch land again.