One of the more bizarre features of London’s story as a city that has evolved over two millennia is that, for almost 1,700 years, it could boast only one bridge across the River Thames. Raised at the end of the 12th century, London Bridge had four-storey houses, a chapel dedicated to Thomas Becket and a suite of public lavatories known as ‘common sieges’. Shops opened along its central thoroughfare, which was used as a drove road for livestock, and waterwheels for pumping drinking water were installed under the side arches.

Soon enough London Bridge became a hazard as much as an amenity. Taking a boat through one of its nineteen arches, known as ‘shooting the bridge’, with the wind perhaps in the wrong direction and a five-foot drop into the frothing wash beyond, was a life-or-death experience. Larger vessels bearing cargo for upriver businesses – the brewers, tanners or makers of gunpowder, bleach and vitriol – found no passage beneath; in 1832 the whole venerable edifice was dismantled, to be replaced by the five-arch span crossed by T S Eliot’s sighing, moribund multitudes in The Waste Land.

The new bridge’s principal architect was John Rennie, one of a formidable breed of Scottish engineers bringing speed and connectivity to Regency Britain. ‘Every part of the United Kingdom possesses monuments to his glory’, gushed a contemporary, ‘and they are as stupendous as they are useful.’ An earlier Rennie project