Thousands of Christmas journeys have been hit after a day of chaos on the rail network, with more than one in ten journeys delayed across England and Scotland.
A total of 13% of train journeys have been cancelled or delayed as networks were affected by a combination of bad weather, signal problems and staff shortages, Network Rail said.
The south of England was one of the worst affected regions, with more than a quarter (26%) of Southeastern trains not leaving on time following signalling problems at Gillingham and flooding on tracks between Folkestone Central and Dover Priory, which caused all trains between those stations to be cancelled.
A Southeastern rail spokesman said: "Subsidence to track ballast on the rail track near Dover Harbour following flooding means we are unable to run trains between Folkestone Central and Dover Priory for the rest of the day. Network Rail are on site checking damage to the sea wall by the track."
Meanwhile, Southern rail contacted passengers to tell them that journeys had been disrupted by a shortage of train crew, and warned that services will be affected for the rest of Christmas Eve.
Rail companies have been bombarded by messages on social media from angry travellers, with some vowing never to use the rail service again at Christmas.
Duncan Bannatyne, the businessman and I'm A Celebrity contestant, was delayed on his journey from King's Cross, and asked if he could transfer to an earlier, delayed train.
When told by a Virgin Trains employee that would not be possible, he disagreed in typically bullish style. "If 2 trains are say in a station & doors are open passengers can walk from 1 train to the other DUUUH," he tweeted.
One user, Kyle Howett, said on Twitter that "Waverley (Edinburgh) looks like a riot scene because they cancelled the London train".
Anna Roberts said: "Oh hi @VirginTrains will your 15.30 to Edinburgh ever go or will I just live on the train like a homeless train witch?"
One user, Christopher Golds, has vowed that "Christmas will be cancelled" before he ever gets the train down to Sussex at Christmas again.
Others are trying to look on the positive side, with Andrew Reeves-Hall tweeting that it will be his "Christmas eve adventure" to get his cancelled journey refunded by South West Trains.
Engineering plans over Christmas are expected to cause further disruptions. Network Rail said 20,000 of its workers would carry out almost 500 improvement projects across Britain over the festive season, which will sever train links to both Gatwick and Heathrow Airports.
From 10pm tonight, there will be no Gatwick Express or Southern services between South Croydon and Redhill until Monday January 4. At Heathrow, the normal one-day closure on Christmas Day will be extended by three days due to Crossrail works.
Some train services will finish earlier this evening to make way for works, with all Southeastern services at Charing Cross, Cannon Street, London Bridge and Waterloo East finishing at 8pm.
Work to replace a major railway junction at Purley will also cut off direct services from Brighton to the capital.
The West Coast Main Line will be closed between Crewe and Stafford from Friday until Tuesday, while there is also a shutdown on lines from London Liverpool Street to Colchester, Ipswich and Norwich.
Further information about disruption to rail services can be found on the National Rail Enquiries website.
Network Rail chief executive Mark Carne has said he is ''acutely conscious'' that people want to use the railway over Christmas to see their friends and families.
He added: ''Passengers have shown themselves to be incredibly understanding of planned improvement work and I'd like to thank them in advance for their support and understanding as we deliver the big improvements that the travelling public want to see.''
There was severe disruption last year when engineering work on the lines from King's Cross and Paddington overran, delaying travellers on the first Saturday after Christmas. Passengers wanting to use the East Coast main line were advised to go to Finsbury Park in north London, which led to serious overcrowding.
This year, Transport Secretary Patrick McLoughlin said officials were "determined to apply common sense" in a bid to minimise disruption.
As well as the planned works, the Rail, Maritime and Transport (RMT) union said Britain's "overstretched" railways had suffered from signal failures, staff shortages and overcrowding in recent weeks.
Other unions have claimed rail travellers have suffered a "pre-Christmas fortnight from hell" because of a series of unexpected problems on the network.
Today was expected to be the busiest day of Christmas on the roads, with more than four million festive journeys, the RAC has predicted.
The number accounts for almost half of all car journeys expected to be made over the festive weekend, on the same day as train services across the UK finish early.
RAC Traffic Watch spokesman Rod Dennis said: "Around 11 million separate Christmas-related car journeys will take place between Christmas Eve and Boxing Day, and this is consistent with previous years."
An AA poll of more than 29,000 motorists also found that 36% planned to cover distances of more than 20 miles (32km) today.
Widespread engineering plans set to go ahead over the Christmas period are also likely to cause disruption for British travellers, despite a scheme to remove roadworks.
Nearly 400 miles (644km) of works were removed ahead of the travel rush yesterday, but a total of 184 schemes will remain in operation.