Hundreds of journeys home for Christmas have been hit by signalling problems and flooding on tracks in the south east of England.
Signalling problems at Gillingham left services disrupted from central London on busy Southeastern commuter lines, while flooding caused all trains between Folkestone Central and Dover Priory to be cancelled for the rest of the day.
Across the country, more than one in ten journeys were delayed (13%) according to a National Rail spokesman. On Southeastern trains more than a quarter were either delayed or cancelled with 74% running on time.
The 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. We are running bus replacement services between Folkestone Central and Dover Priory to make sure people that live between these two stations are able to get home but we would advise passengers to please check before travelling and leave extra time for their journeys."
Today is 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.
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.