Hundreds of thousands of rail passengers in the region are facing 10 days of severe disruption because of massive engineering works over the festive break.
Around 20,000 Network Rail staff will be on duty upgrading track and signals.
Some of the biggest disruption will be to the Brighton line, at London Bridge. The lines to Paddington. Gatwick and Heathrow will be badly hit.
Network Rail say they have learned the lessons from last year when work ran late, causing chaos. They insist it is the best time to do the work as fewer than half the usual one million passengers who travel by train in our region every day use the service.
Greater Thameslink Railway: Work at Purley means the Brighton main line will close form late on Christmas Eve for 10 days with no direct services from Brighton and Gatwick to London able to use it. Trains that do run to Gatwick from London will use an alternative route, adding an extra hour to the journey. Passengers are strongly advised to travel to East Grinstead and take shuttle buses to Gatwick. The work will replace one of the most unreliable junctions on the line.
Southeastern: London Bridge will be closed along with Cannon Street, Waterloo East and Charing Cross from the evening of Christmas Eve for 10 days. This will hit tens of thousands of passengers. Services will be diverted to Victoria where possible.The work is part of the Thameslink upgrade.
South West Trains: Services between Weymouth and Southampton will be disrupted from the last train on Christmas Eve for 10 days. Passengers are advised to check with the companies. The work will improve the infrastructure in Dorset.
Great Western: The line between Slough and Paddington will close from the evening of Christmas Eve for four days, reopening on 29 January. Then until 3January only two of the four lines into the station will operate. Many services will be diverted to Waterloo or Marylebone.The work is for Crossrail and the Great Western electrification.
Heathrow Express: No service on 25 - 28 December. From December 29 - 3 January services run every 30 minutes. The work is for the Crossrail scheme.
Chiltern: Chiltern will be the only operator running services on Boxing Day. It has no planned works.
No services will run on Christmas Day, and services on Christmas Eve will finish earlier than usual.