M25 Greater London – Queuing traffic on M25 anticlockwise between J29, A127 (Romford) and J24, A111 (Potters Bar).
Flights have been cancelled at Heathrow Airport due to freezing fog covering much of southern England.
About 100 flights have been affected at Heathrow, while Gatwick says it is monitoring the situation.
Dense fog has reduced visibility to 100m at airports across the capital including London City and Stansted.
The Met Office’s yellow warning for fog – meaning be aware – covers London, the South West, the South East and some eastern parts from 01:00 to 10.30 GMT.
Steven Keates, of the Met Office, said there would be “dense freezing fog”, particularly in the early hours.
Heathrow warned passengers to check flight updates before travelling.
A message on Heathrow’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.”
A130 in North Benfleet closed southbound between Fairglen Interchange and Sadlers Farm Roundabout, because of ice and surface water.