M4 motorway London to Heathrow section closed
7 July 2012 Last updated at 10:42 BST
The main motorway link from London to Heathrow Airport has been closed to all traffic after a crack was found in a "sensitive area" of the road structure.
The M4 is shut between junctions one and three and is expected to remain closed for up to five days.
The BBC's Tim Reid reports from the M4.