Olympic Stadium: Work starts on new roof
Work has begun to install a new roof on the Olympic Stadium as part of a £190m transformation of the east London venue.
At twice the size of the previous roof, it weighs more than 6,000 tonnes and will cover every seat in the stadium.
The roof is designed to improve acoustics and will be ready in time for the 2015 Rugby World Cup.
The structure covers 45,000 sq m and is believed to be the largest cantilevered roof in the world.
Stuart Fraser, stadium transfer project director for construction company Balfour Beatty, which is installing the roof, said the stadium was "technically challenging".
New floodlights will be installed, along with hospitality suites, toilets and turnstile areas. Costs have risen by £36m because of the need to strengthen existing steelwork.
Work on the stadium is due to be completed in spring 2015, and Premier league team West Ham United are set to move to the arena in 2016.