The Highways Agency said it decided to keep the Boston Manor Viaduct closed because during works it found a crack in a "sensitive location", which requires it to be kept closed until it is repaired.
Diversion on the A312 and the A4. Drivers are being advised to allow extra time for their journeys.
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Holly has the latest forecast for the east of the region.
The forecast for the west of the region from Holly.
Holly has the latest forecast for the west of the ITV Meridian region.