A spokesperson for Crossrail has told ITV London that the worker who has died was spraying concrete when a piece of concrete from the ceiling fell and hit him.
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His top speed is believed to be the highest ever recorded in the UK by a rider carrying a pillion passenger.
The mayor took time out from City Hall to join Conservative party workers handing out leaflets in Uxbridge and South Ruislip.
No matter where you look, London's population is getting older - with the exception of one of the capital's boroughs.