Network Rail has warned east London train travellers it has a "significant" programme of engineering work planned this Christmas.
The company, which runs Britain's rail infrastructure, has announced where it is carrying out improvements and when over the festive season.
The lines around Liverpool Street station are "a major focus" of upgrade work, a spokesperson said.
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No trains will run in or out of the station between the end of service on Christmas Eve (December 24) until the start of service on January 3.
The work includes introducing a new power system that will supply overhead lines between Bow and Shenfield. This will "support the long-term reliable running of both Elizabeth line and Greater Anglia trains", the Network Rail spokesperson explained.
Replacing an old bridge near Bethnal Green and refurbishing numerous sets of points on the approach tracks into Liverpool Street is also part of the planned work.
There will be no Elizabeth line trains between Paddington and Shenfield on December 27, and between Whitechapel and Shenfield between December 28 and January 2.
The Liverpool Street work will also see Greater Anglia put on rail replacement buses which will run to Newbury Park Tube station from Ingatestone on the Norwich mainline and from Billericay on the Southend Victoria line (except on December 27 when a replacement bus service will run between Southend Victoria and Newbury Park).
National Rail tickets will be accepted on Central line services between Newbury Park and Stratford / Liverpool Street.
London Overground services will also not run into or out of Liverpool Street from December 27 to January 2, while the Romford to Upminster branch line also will not run between these dates.
Other work taking place will see no service on December 27-30 on the line between Gospel Oak and Barking Riverside.
Transport for London says a replacement bus will run between Barking and Walthamstow Central.
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Ellie Burrows, Network Rail’s route director for Anglia, said: “Work over Christmas is critical for upgrading and maintaining the railway ahead of the new year, with our teams out on track while so many of us are having fun and relaxing in our homes.
“We have a significant Christmas programme this year, particularly on the lines into Liverpool Street. I hope passengers can understand the need for the upgrades."
Work is also taking place which will impact passengers on c2c's Ockendon and Rainham lines.
No trains will run on the latter on December 27, 28 and January 1, with a replacement bus service operating between Upminster and Grays.
The former will see rail replacement buses run between Chafford Hundred and Pitsea on the same dates.
Rob Mullen, c2c managing director, said: “We are aware that weekend engineering has particularly affected customers on our Rainham and Ockendon lines over the last couple of months.
"However, overhead line issues are very disruptive so these works over the festive period will help improve the resilience of this vital equipment.
"We would ask our customers travelling over the festive period to check before they travel."
For more information, visit greateranglia.co.uk, c2c-online.co.uk and tfl.gov.uk.
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