UPDATE: Finsbury Park station has been closed due to over-crowding.
Snow and blizzards have swept through large parts of Britain, leaving many travellers stranded.
Sleet and snow hit the north of England, the Midlands and Scotland and the Met Office has warned that nearly all the UK has been gripped by ice.
The freezing weather has brought treacherous conditions to roads, with many motorists in Sheffield forced to abandon their cars after becoming snowed in.
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Compounding the travel chaos even further on Saturday is overrunning engineering works at one of the country's busiest rail terminals.
Trains in and out of London King's Cross have been cancelled because of overrunning Network Rail engineering works north of the station, with a reduced service tomorrow.
Queues outside Finsbury Park (which is now closed due to overcrowding) after Kings Cross trains cancelled. Stranded! pic.twitter.com/em2gHAYB1Q— Kieran Gill (@kierangill_DM) December 27, 2014
Passengers travelling with East Coast, First Hull Trains, Grand Central and Great Northern face major delays on many services, Network Rail said.
By lunchtime the mayhem had stretched north to Finsbury Park, where large crowds of rerouted travellers forced a temporary closure.
An East Coast spokesman said: "We apologise for the continued disruption to journeys today, after Network Rail engineering work north of London King's Cross station was not completed as planned.
"Our very strong advice to customers is to avoid travelling today, and to defer travel to another date. Tickets dated for today will be valid tomorrow and on Monday.
"Finsbury Park station was temporarily closed for a short period on police advice and to allow time for the backlog of passengers to be cleared. Every available East Coast resource is being made available to support our customers."
He said passengers should check the East Coast website, follow its Twitter account or call National Rail Enquiries for updated information.
Meanwhile overrunning engineering works between London Paddington and Hayes & Harlington caused delays of up to an hour, National Rail Enquiries said.
Those delays were expected to last until at least 1.30pm.
Najib Mohamed, 18, from north London, said he had to make other arrangements after arriving at King's Cross this morning expecting a train to take him to work outside of the capital.
He said: "It is usually very, very busy here, but not today. I am supposed to be working as a fundraiser today and getting told where to go once I get here, but there are no trains so I think I might just go back to bed."
Network Rail said the engineering work near King's Cross was part of a £200 million Christmas investment programme, with most services expected to return to normal on January 5.
It is one of 300 projects being undertaken over the holidays at 2,000 sites up and down the country by 11,000 engineers.
Experts said more snow could hit higher Britain today, but warned the main threat came from ice.
Liverpool's John Lennon Airport and Leeds Bradford International were forced to close last night as snow was cleared from the runways, but have now reopened.
More than 100,000 homes were left with power shortages as heavy snow wreaked havoc on electricity cables.
#KingsCrossTrains miserable journey from Northallertion, now stationary outside Potters Bar!— andy price (@entjourno) December 27, 2014
A Western Power Distribution spokesman said 36,000 customers were left without power and another 69,000 had short interruptions to supplies.
Staff worked through the night to reconnect customers, but around 3,000 in the East Midlands were still affected.
The north of England and the Midlands were the worst affected by the snowstorms, with 11cm (4.3in) falling in Leek, Staffordshire.
Nottinghamshire and Bingley, near Bradford, were hit by flurries of up to 7cm (2.8in).
Many drivers became marooned by heavy snow in Sheffield, Chesterfield and the Peak District.
A spokesman for the RAC said drivers in these areas were experiencing "big problems".
#kingscrosstrains BRING ME THE HEAD OF SOMEONE SENIOR AT NETWORK RAIL— E. M. Larkin (@emlarkinwrites) December 27, 2014
He said: "We are rescuing people who are bogged down in snow there. That seems to be the biggest area of problems in the UK. We are seeing higher volumes of calls than we would usually get on a Saturday this time of year.
"Some motorists are abandoning their vehicles."
Drivers took to Twitter to complain of the long queues and post pictures of roads blanketed in heavy snow.
At around 2.30am one driver said he had been in a queue for more than four hours.
Declan Pitts posted a picture of a snowy country road and wrote: "I'm alive after 3 hours of crazy snow torn driving across what seems like the whole of England."
A coachload of people travelling from Sheffield to London had to take refuge in a church after their bus became stuck in the snow before leaving the city, passenger Chloe McIntosh told the BBC.
She said: "Some people from the houses nearby have come and offered us tea. Then they opened up the church."
Motorists have been advised to check routes before embarking on a journey and to avoid travelling in snow-hit areas if possible.
Four flights into Liverpool from Malta, Berlin and Bucharest were diverted to Manchester Airport, while a fifth from the Isle of Man returned to the island's airport, a John Lennon Airport spokesman said.
Police warned of hazardous conditions last night, especially in Staffordshire and Cheshire, with several roads impassable.
Staffordshire Police tweeted: "Reports of difficult road conditions across Staffordshire due to snow, please only travel tonight if necessary."
Cheshire Police said: "Roads around Delamere/Frodsham looking quite treacherous due to weather, please drive with care."
Leicestershire Police tweeted: "Snow causing disruption in the north of the county. Please only travel if absolutely necessary and avoid A1 as large vehicles are stuck."
The Met Office has issued amber warnings for snow, ice and wind across much of Britain.
A Met Office spokesman said another 1cm-2cm of snow could fall on higher ground in the Pennines, Yorkshire Moors, East of England and west of England as wintry showers pass through the country.
He added: "The worst of the snow has passed through. There is quite a bit of ice, especially over the higher ground in the north of England.
"Overnight tonight ice is going to be more of a problem."
The snow made conditions difficult for some of yesterday's football matches, including in the West Midlands as West Bromwich Albion lost 3-1 to Manchester City in a game played in a blizzard at The Hawthorns.
The Met Office had earlier said there was a 90% chance of severe cold, ice or snow in parts of England between this afternoon and New Year's Eve.
Christmas night was the coldest night of the year so far, with minus 8.5C (16.7F) recorded at Braemar in Aberdeenshire.
Temperatures could drop as low as minus 10C (14F) in some places at the start of next week as the cloud and wet weather gives way to clearer skies.
A spokesman for Leeds Bradford International Airport said four flights into the airport had to be diverted and two outbound flights cancelled last night due to the snow, affecting nearly 1,000 passengers.
The airport reopened at 12.30am, and while there were some delays early this morning flights are back to normal, a spokesman said.
A Department for Transport spokesman said: "As winter weather grips some areas of the country we would advise people intending to travel to check weather and local conditions before they set out.
"The Highways Agency and local highway authorities across the country are working hard to ensure disruption is kept to a minimum.
"Passengers travelling into or out of Kings Cross affected by overrunning engineering work should check with National Rail enquiries for service information."
Passengers at Manchester Airport complained of delays this morning.
Laura Thornhill wrote on Twitter: "What's the delay? Been sitting on the plane for over an hour - no update no refreshments #poorcustomerservice."
Sian Perrin wrote: "Waiting for de-icing truck & been told there aren't enough! Will now miss connection to Prague. @lufthansa doing all they can."