Work began yesterday to save Isambard Kingdom Brunel's first iron bridge, which has been hidden for decades near Paddington station in London.
The bridge, which was found encased inside a modern brick road bridge over the Grand Union Canal last summer, is being dismantled to make way for a new traffic scheme.
With its two cast-iron arches spanning the canal, the unique structure is the earliest of eight surviving Brunel iron bridges in the country. The chance discovery of notes in Brunel's private work book was the first sign of the bridge's existence.
Dr Steven Brindle, English Heritage's inspector of ancient monuments for London, found the engineer's designs and letters dating back to 1838 while researching the history of Paddington station. The records led Dr Brindle to inspect Bishops Bridge Road where he found Brunel's structure preserved under brick parapets with parts of it exactly matching his original sketches.
The discovery came before an agreement was finalised to demolish the bridge as part of a £62m road improvement project. Westminster City Council halted demolition plans and ordered the bridge to be dismantled and moved from the site.
Dr Brindle said there was the "elation coupled with shock'' when it was realised that the bridge had survived but that it was due to be demolished.
The council is to restore and relocate the bridge, possibly as a footbridge near where it originally stood. The work is due to be completed by 2006.