Britain's transport network could be brought to its knees today as heavy snow is expected to blanket the UK.
Much of the UK has woken up to a thick covering of snow, and up to 12in (30cm) could fall on higher ground.
Travel companies have warned of widespread travel disruptions, and train firms have put out revised timetables. Southern, Greater Anglia, South West Trains and the Eurostar are all running amended services on a number of routes or with speed restrictions because of the snow.
Gritters have been out in force, and the Highways Agency has issued an amber alert, advising motorists to take extra care and check weather forecasts before they travel.
Weather experts warned it would be "bitterly cold" in England, with temperatures likely to remain below zero. Most of the UK is likely to be covered with between five and 10cm of snow. People in the South West will experience blizzard conditions throughout the morning, with winds of at least 30mph across Devon and Cornwall.
The Met Office has issued a "red" severe weather warning for heavy snow in upland parts of south east Wales, which is set to experience the worst of the weather. Merthyr Tydfil was among the worst hit areas, with reports of panic buying causing some local shops running out of stock. Drifting snow of up to 12in (30cm) is likely to cause severe disruption, the Met Office said, and warned people to avoid all but essential journeys. Amber alerts were in place for the Midlands, London and the South, the east of England, the South West, the North West and Northern Ireland.
With speed restrictions in place, Eurostar axed four trains today - the 6.50am and 2.04pm London to Brussels trains and the 8.52am and 5.56pm Brussels to London trains. South West Trains scrapped services between Ascot and Ash Vale, between Virginia Water and Weybridge, between Salisbury and Bristol Temple Meads and Guildford and Leatherhead. A problem at a level crossing caused by snow affected services operated by the East Midlands Trains and Greater Anglia train company, with delays between Ely and Norwich.
On the roads, there were severe problems in South Wales, with the M4 closed between Bridgend at junction 36 and Pyle at junction 37. A number of A roads in South Wales had to be closed. Motorists were warned of poor conditions on the M4 in Carmarthenshire, South Wales, and on the M48 in Monmouthshire and on the A48(M) near Newport, while the snow caused tailbacks in Cardiff. There were also hazardous conditions reported on the A4136 in Brierley in Gloucestershire and also on the A4151 in Littledean.
Around 70 flights were cancelled at London's Heathrow Airport. A spokesman said: "This is primarily because of problems at other airports. Obviously the snow is affecting the whole country and it just means there's a knock-on effect here." The airport has extended the length of time between one flight and the next for safety reasons. A statement on Gatwick's website read: "Snow is expected at Gatwick this morning and during the course of today. Please check the status of your flight with your airline before travelling to the airport. Allow extra time for your journey to Gatwick as road and rail networks may be impacted."
British Airways cancelled more than 60 of its flights but said this figure was likely to change during the day. Southampton Airport cancelled flights this morning as it attempted to clear snow from the runways. Some flights at Newcastle Airport were cancelled and the runway was closed at Jersey Airport. Glasgow Airport reported disruption to some flights.