Emergency engineering work has taken place at Wimbledon to repair a broken rail on the track that runs through platform 5. The lines have now reopened, but services are being severely disrupted as a result of the speed restriction in place.
It means a significantly reduced South West Trains service will run through Wimbledon this morning.
Delays are expected until lunchtime. Passengers are advised to check before they travel.
Fog is expected to cause some disruption to flights at Heathrow tomorrow (Jan 23). Please check with your airline prior to travelling.
Fog is affecting the region's airports. Gatwick and Heathrow are on 100 metres visibility. Fog and low visibility is also affecting flights to and from Southampton Airport throughout Monday morning. Passengers are advised to check before they travel.
Road users are also being warned of difficult driving conditions after freezing conditions overnight.
In England a low of minus 6.2C (21F) was recorded in Northolt, around 10 miles from Heathrow.
A message on Heathrow Airport's website said: "Foggy weather across London is expected on Monday 23 January and some passengers may experience disruption to their journey as a result.
"Heathrow advises passengers to check their flight status with their airline before coming to the airport. Heathrow's top priority is the safety of passengers and we apologise to those whose travel has been affected."
Mr Wilson said temperatures will struggle to top 0C (32F) in the worst affected areas on Monday, where fog is likely to persist.
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