London Bridges: 19. Rolling Bridge, Paddington

Heading west from the Helix Bridge, the next footbridge at Paddington Basin is the Rolling Bridge, easily the best known of the set, and justifiably so.

I would guess few of my readers will be unfamiliar with this bridge, as it is one of the most remarkable and audacious footbridge designs from the last decade. As with the Helix Bridge, it's something of a white elephant, spanning a very small side-arm of the canal, which goes nowhere and has no real reason for continued use by boats. The bridge is useful in providing a direct route along the edge of the main canal basin, but it doesn't really need to open.

Nonetheless, it does open, every Friday at noon. Sadly, I was there on a different day of the week. The opening mechanism is unique: the bridge slowly curls up from its level position, ending up in the form of an octagon when fully open. Its initial form, which broadly resembles a modified Warren truss, is distorted by extending eight hydraulic cylinders in each of the trusses.

Most moving bridges operate on the principles of translation (lifting and retractable bridges) or rotation (bascule and swing bridges). Very few adopt the principle of transformation, indeed about the only other examples which come to mind are Schlaich Bergermann's folding bridge at Kiel and arching bridge at Duisburg.

There is a sense that the Rolling Bridge's design is just a gimmick, but on balance I think not. It's delightfully inventive, playfully so, with the resemblance to a curling caterpillar responsible for a significant cuteness factor.

It was designed by Thomas Heatherwick, with structural engineering by Packman Lucas and SKM Anthony Hunt. The steelwork was fabricated by Littlehampton Welding. It cost £330,000 in 2004, which seems a lot for a 12m long bridge, but was surely worth it.

Up close, the detailing is nicely done, although the bumpy profile of the top rail in the at-rest position looks  a little odd. It's often a problem with "iconic" opening bridges that their sense of spectacle is lost when they are closed. With the Rolling Bridge, it still retains a sense of potential, like a muscle tensed and ready to flex.

Further information:

• Google maps / Bing maps
• Structurae
• Wikipedia
• movablebridges.org.uk
• Discover Paddington Waterside (walking tour)
• Footbridges (Baus and Schlaich, 2008)
• An Encyclopaedia of Britain's Bridges (McFetrich, 2010)