Disruption to rail services is worsening as Covid forces staff off sick or isolating, coupled with industrial action.
Southern announced that none of its trains will run to or from London Victoria until January 10 due to "coronavirus isolation and sickness".
London Victoria is one of the UK’s busiest stations, and is normally connected by Southern to locations such as Brighton, Eastbourne and Portsmouth.
Elsewhere, CrossCountry urged customers to avoid travelling on New Year’s Eve as a strike by members of the Rail, Maritime and Transport (RMT) union means it will run "a very limited timetable".
The dispute involves train managers and senior conductors in a row over the role of guards.
What train services have been affected and where?
No services will run to or from London Victoria, Battersea Park, Clapham Junction, or Wandsworth Common until January 10.
Planned re-signalling work at London Victoria had already resulted in most Southern trains due to serve the station between December 27 and January 3 being diverted to run to and from London Bridge.
The firm will not operate any trains between:
Aberdeen and Edinburgh
Glasgow Central and Edinburgh
Derby and Nottingham
Peterborough and Stansted
Cheltenham Spa and Cardiff Central
Newton Abbot and Paignton
Plymouth and Penzance
A "heavily reduced service" will be in place between Edinburgh and Plymouth; Manchester Piccadilly and Bournemouth; and Birmingham New Street and Peterborough.
Many other operators in addition to Southern have cancelled trains due to the impact of the pandemic.
They include Avanti West Coast, CrossCountry, Greater Anglia, London North Eastern Railway, Northern, ScotRail, TransPennine Express and Transport for Wales.
RMT members employed by Gate Gourmet are also involved in a strike at Edinburgh Waverley on New Year’s Eve as part of a long-running dispute over allegations of bullying.
RMT general secretary Mick Lynch said: “The disruption to services from the New Year’s Eve strike action is wholly down to these greedy private companies on our railways seeking to squeeze out every penny they can by hammering down on safety, jobs and workplace dignity.
“Our members at CrossCountry and Gate Gourmet are standing up for all rail workers as we expect a torrent of attacks on jobs, pay, safety, pensions and working conditions in 2022.
“We are ready for a new year of campaigning and action on all fronts.”