Britons are facing Christmas travel chaos and a mad dash on the 'bubble' deadline as swathes of the rail network will be shut or running reduced services.
The four UK nations have agreed a relaxation of coronavirus restrictions to allow them to mix in a 'bubble' with three other households between December 23 and 27.
However, those who need to travel home by rail when the five-day window ends could face significant disruption amid fears train services could be crowded and social distancing will be difficult.
After a complete shutdown on Christmas Day, most of the rail network will be shut on Boxing Day with "a very limited number of services" will be running on "a small number of routes".
A majority of the rail network is shutting on December 27, when a reduce Sunday service will already be in place.
People travelling into Northern Ireland to form a bubble have until December 28 after being given an extra day to allow time for journeys.
Tens of thousands of Britons are expected to delay their journey home until the last day of the reprieve.
The Rail, Maritime and Transport (RMT) union has said it expects a "surge" in passengers over the five days.
Rail industry body the Rail Delivery Group (RDG) said that although there is "no concern" of overcrowding on train carriages, thousands of services are expected to run daily to cope with more passengers.
There will be disruption on major routes linking London with Edinburgh, Cardiff, Bristol, Manchester, Liverpool, Sheffield and Newcastle, and lines that run to major airports around the capital.
Services run by LNER, Great Western Railway, Cross Country, Greater Anglia, South Western Railway, Avanti West Coast, London Northwestern, East Midlands and Transpennine Express will be among those be affected.
Major engineering work taking place in the London King's Cross area will close all lines from December 26 to December 30, said Network Rail.
The routes affected are Grand Central, Great Northern, Hull Trains, LNER and Thameslink.
South Western Railway services will be disrupted by engineering work that will shut various lines between London Waterloo and Clapham Junction from December 27.
Improvements between London Liverpool Street and Shenfield from December 27 will also result in closures affecting Greater Anglia and TfL Rail services.
Great Western Railway services will face disruption between Cardiff Central and Portsmouth Harbour, and London Paddington and Bristol Temple Meads.
There is no service on the Transpennine Express on Boxing Day.
There will also be reduced service on Southern, ScotRail and London's Underground and Overground networks.
The Government has pledged to give Britons more options for travelling over Christmas, with the first day of the 'bubble' now 11 days away.
Network Rail chairman Sir Peter Hendy has been appointed Christmas travel tsar to oversee transport plans for the festive period.
Action being taken to smooth journeys includes shortening rail engineering work and longer trains being operated on some routes.
Transport Secretary Grant Shapps was urged to put on more trains before the Covid-19 restrictions are relaxed.
Mr Shapps has urged travellers to "look very carefully at the transport route they take” when they cross the country.
He acknowledged there would be significant disruption, but added that engineering works cannot be changed because they had been planned for months.
Christmas coach services have been given a £3million boost by the Government to help firms such as National Express and Megabus to increase capacity.
Highways England will remove 778 miles of roadworks from England's motorways and major A-roads by 6am on December 20 until the early hours of January 4, meaning 96% of its network will be fully open.
The AA has begged councils to remove roadworks to ease delays for families travelling by car.
Drivers are planning 13 million trips to visit family and friends during the Christmas bubble period, a new survey suggests.
The RAC poll of 1,500 motorists indicated that December 23 will be the busiest day for festive road travel, with 3.1 million journeys.
Christmas Eve and Christmas Day are predicted to see 2.8 million and 2.5 million trips respectively, which is similar to levels seen in recent years.
Many of these are expected to be local journeys.
A further 2.1 million car journeys are expected between December 23 and 27 but respondents were not sure about their exact travel date.
Only 1.6 million trips on Boxing Day are planned, down from an average of 4.5 million over the past five years.
