People who hope to use Britain's railways to stay with their families for Christmas will face major disturbances due to engineering.
Network Rail has warned that some routes will have significant changes in normal services, as it encouraged passengers to plan their travels as early as possible.
However, some timetables will only be confirmed six weeks in advance, instead of the standard 12.
Announcement comes in the back of months with struggles for rail passengers who have met delayed improvement projects and unrestrained launch of new trains and services after "outrage " investment.
:: Scroll down for affected lines and drives.
Some of the festive improvement work starts on December 23 – one Sunday – to give the engine "three clear days to make uninterrupted progress."
Despite the changes, Network Rail said there would be less general disturbance than last year's Christmas season because most workers are scheduled for when no train is scheduled to run, such as Christmas Day and Boxing Day.
A number of lines serving London's main stations and airports will be blocked.
Andy Thomas, CEO of Network Rail's strategic operations, said that thousands of workers will be "working 24 hours to deliver important upgrades" as part of the $ 50 billion upgrade plan.  He said that it will make the services more reliable.
Thomas added: "We know that our railroad is up to 50% quieter than usual at the festival so that we take on and deliver this major transfational arrangements at this time of year minimizes our influence on passengers who show research, Estimates the need for such activity. "
] These are the lines and stations that will be affected:
:: London Paddington will have major work between 23 and 31 December.
:: Heathrow Express suspended between 23 December 25 December and 30 December.
:: Great Western Railway Train will end at Slough or Reading.
:: Clapham Junction will be extremely busy from December 23 to New Year's Day because platforms 9 to 19 in London Victoria will be closed.
:: London Bridge will be severely affected, without Gatwick Ex express train and most southern services will be diverted to and from the station.
:: Stations between Bedford and Kettering will be affected as track enhancements take place from 24 December to 1 January.