Iron Bridge wrapped up for Christmas

The Iron Bridge
Image caption Early work on the bridge is focusing on cleaning and then conserving the ironwork

The Iron Bridge in Shropshire has been wrapped up for Christmas while repair work on it continues.

The £3.6m conservation project is English Heritage's largest since becoming independent of government and is due to take another year to finish.

The covers have been put up to protect the structure as the early work focuses on cleaning it.

Engineers working on the project said they were already finding problems caused by previous repair attempts.

Image copyright English Heritage
Image caption English Heritage is planning to set up a scaffold walkway to give members of the public a chance to see the conservation work close-up

Spencer Smith, archaeology officer at the Ironbridge Gorge Museums Trust, tweeted that an earlier attempt to repair faulty ironwork supporting the railings had "failed" and meant the current conservation team knew to avoid the same approach.

Completed in 1779 over the River Severn, the Iron Bridge was the first single span bridge in the world to be made of cast iron. English Heritage described it as a "turning point in British engineering".

However, much of the cast iron has cracked over the years and further damage was done in an earthquake in the 19th Century, which pushed the sides of the gorge closer together.

English Heritage said the apex of the bridge was today 10cm higher than when it was built.

Image copyright Aaron Chown / PA
Image caption An earthquake in the 19th Century pushed the two sides of the gorge the bridge spans closer together
Image caption Surveys have shown the Iron Bridge is under threat from cracking due to stresses in the ironwork dating from the original construction
Image caption The bridge, built by Abraham Darby III and designed by Shrewsbury architect Thomas Farnolls Pritchard, weighs 378 imperial tons

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