Cold weather causes travel disruption across the UK
Traffic in the Home Counties ground to a halt amid ice and slush
Winter weather is continuing to cause disruption across the UK with road, rail and air travel all affected.
Channel Tunnel services remain badly affected after Eurotunnel closed its car shuttle service to new passengers.
British Airways cancelled all European and UK domestic flights leaving Heathrow after 1900 GMT.
Many roads in the Home Counties are gridlocked and the AA said London and the South East were hotspots for vehicle breakdowns.
Luton airport is closed until 0030 GMT and London City airport is shut. Stansted airport is open but flights may be subject to delays or cancellations.
Easyjet said it had operated over 80% of its flights, "albeit with some delays", over the last five days despite the weather, but added that further snow on Monday night could result in continued flight disruptions.
A Met Office severe weather warning is in place for ice in many parts of the UK, where snow freezing on the ground is causing treacherous conditions.
Temperatures are expected to fall to 1C (34F) in central London overnight, -4C (25F) in Newcastle, -3C (27F) in Glasgow, -4C in Manchester and -1C (30F) in Cardiff.
In Wales, 180 schools and nurseries had to close, while the M4 was shut after a crash.
Many minor roads are treacherous - they're like ice rinks - with numerous shunts and cars stuck in ditches
Up to 5cm (2in) more snow is expected in the south and east of England, spanning from Lincolnshire down through Hampshire, followed by freezing conditions.
The weather had its greatest impact on Channel Tunnel services, where Eurostar cancelled trains to mainland Europe for the third day, while Eurotunnel closed its shuttle car service to new arrivals after its Folkestone terminal reached "saturation point".
Eurostar said it hoped to resume a limited service on Tuesday.
Airport problems
Passengers at Heathrow's Terminal 5 have reported large queues as people attempt to make alternative arrangements following BA's decision to stop its evening flights.
People are said to have been offered coach trips to places such as Newcastle to replace their cancelled flights.
At Manchester Airport, where flights were suspended overnight, the backlog of flights had been cleared by Monday afternoon.
Passengers at Bristol and Southampton airports have also experienced delays.
Bad weather in North America and Europe delayed flights arriving at Heathrow and Gatwick airports for up to six hours.
A spokesman for Gatwick said the runway had re-opened at 1954 GMT - having closed at 1519 GMT - and that staff were now working to get through the backlog of flights but the most affected airline, Easyjet, had cancelled a number of services.
Passengers travelling from Gatwick are advised to allow extra time for their journey to the airport and contact their airline for the latest flight information.
Passengers intending to use Luton airport are advised to contact their airline for more information.
Aberdeen and Inverness airports reopened after being closed on Monday morning, but delays and cancellations continued at both airports, and at Glasgow airport.
Treacherous roads
Domestic rail services across the UK were delayed and buses replaced trains in many areas.
Southeastern trains said it would be operating a Saturday timetable service on mainline, metro and high-speed routes on Tuesday, with a normal weekday service for Thameslink trains run via Blackfriars.
The company said there would be additional high-speed services through the day and a shuttle service between London Bridge and Cannon Street during the morning and evening peak times.
At the height of the morning rush hour, six vehicles collided on the M4 in Wales at junction 48 near Llanelli.
In Pembrokeshire, one man was taken to hospital after being trapped in his van after it overturned near Haverfordwest.
Roads in the north west of Northern Ireland were particularly treacherous, the Roads Service said.
Black ice affected Londonderry roads, including the Foyle bridge.
The RAC said by 1330 GMT it had attended more than 7,000 breakdowns, 32% more than on a typical cold Monday morning.
It said the worst affected areas were East Anglia, Yorkshire, north-east England and the West Midlands.
Roads record
The AA said it had extra patrols out on duty and was bringing in extra Land Rovers to rescue people in inaccessible areas.
It also said that Monday had been its busiest day on the roads in 10 years, after it had attended more than 20,000 breakdowns by 2030 GMT, with call-outs coming in at a rate of 1,200 every hour.
Normally it would expect to deal with about 10,000 vehicles for the whole of a Monday in December.
AA president Edmund King said: "Many minor roads are treacherous - they're like ice rinks - with numerous shunts and cars stuck in ditches."
Thames Valley police have issued guidance for people in their area because of a "hell of a lot of snow" which continues to fall.
They suggest people stay with their vehicles and keep warm but said if anyone did leave their vehicle, they should park safely and put a note on the windscreen with contact details.
Missing man
People have reported major traffic problems in the High Wycombe area of Buckinghamshire, with some vehicles being abandoned.
There are also problems with congestion and abandoned vehicles in Aylesbury and Reading.
Doug Kew, 27, started his three-mile journey home from his workplace in Reading at 1530 GMT, and only arrived at 2130 GMT.
He said the journey was "traumatic", but added: "It's the only time I've seen people wind down their windows and actually speak across the carriageway to each other."
In Essex, fears were growing for a young man who went missing in the freezing weather.
Adam Passfield, 22, was last seen at 0230 GMT on Saturday in Chelmsford, Essex, after an evening out with members of Heybridge Swifts Football Club.
Meanwhile, the government said it would be making cold winter payments because temperatures had been low enough for vulnerable people to qualify.
The Department of Work and Pensions said it spent £30m last week to help mainly elderly people keep warm.
Minister Helen Goodman said: "The payments are automatic so everyone entitled will get them and should not worry about turning up their heating."
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