Severe weather conditions cause chaos on East's roads and railways
The Met Office issued several yellow severe weather alerts due to the wintry conditions
Commuters have faced travel chaos on Monday morning as large parts of the UK were hit by ice, fog and snow.
The Met Office issued several yellow severe weather alerts due to the wintry conditions.
Roads in eastern and south-east England are among the worst hit.
Drivers on the M25 were stranded for several hours due to the UK's busiest motorway being closed in both directions between Junction 23 for South Mimms and Junction 25 for Waltham Cross, both in Hertfordshire.
National Highways said the carriageway will be "cleared and treated as soon as possible".
There are delays of up to 90 minutes on neighbouring stretches of the motorway.
Other roads in the area with long delays include the M11, M2, A21, A27 and A249, according to National Highways.
Sussex Police issued a warning for "treacherous" roads.
The AA advised motorists to adjust their driving to the freezing conditions.
Several rail lines have been shut, with Southeastern issuing a "do not travel" alert to passengers.
There was also major disruption to services run by Greater Anglia, South Western Railway and Southern.
Four children were taken to hospital in a critical condition after being rescued from a lake in Solihull in the West Midlands on Sunday afternoon after falling through ice.
Richard Stanton, area commander for West Midlands Fire and Rescue Service, said: "We know that the weather forecast for the next few days is expected to be bitterly cold, please, adults and children alike, stay away from open water, under no circumstances venture on to ice regardless how thick or safe you think this ice may be."
Gatwick and Stansted airports closed their runways on Sunday to clear snow.