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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ITV News spoke to Nick Channing-Williams who described the freezing conditions on board the car ferry that caught fire earlier today.
Monday's weather for the east with Philippa
Monday's weather for the west with Philippa