Network Rail is urging rail passengers in Sussex to check before they travel this Easter weekend as thousands of engineers will be working around the clock.
The programme of work is part of Network Rail’s railway upgrade plan – a multi-billion-pound investment in the rail network which it says will improve passenger journeys in the months and years ahead.
Southern and Thameslink will run an amended timetable across all routes from Friday 19 to Monday 22 April.
On Friday April 19 and Saturday April 20, Southern will have a reduced service into London Victoria with some services diverted into London Bridge. Gatwick Express services will not run.
On the Sunday and Monday, Southern services between Victoria and Sutton via Crystal Palace will operate between West Croydon and Sutton only. Gatwick Express will run half hourly.
The major investment projects this Easter include:
Laying new track between Thornton Heath and Selhurst from Friday 19 to Saturday 20 April.
In Balham, engineers are replacing switches and crossings, the moveable sections of track that guide trains from one track to another allowing them to cross paths.
John Halsall, route managing director at Network Rail south east, said: “This Easter we’ll be working across the network to improve journeys for passengers.
“There is never a good time to close the railway, but we know that it’s up to 50 per cent quieter than usual over bank holidays, which reduces the impact of our work on passengers.
“I’d like to thank people in advance for their patience and remind them to check before they travel this Easter.”
Thameslink services from the south will terminate at either London Bridge, London Blackfriars or London St Pancras.
From the north, Thameslink services to and from Bedford, Luton and St Albans will terminate in the high level platforms at London St Pancras.
Thameslink Kent services will run between Dartford and Rainham only.
On Sunday there will be no Thameslink services between Blackfriars and Wimbledon via Sutton.
A breakdown of how journeys will be affected can be found by visiting nationalrail.co.uk/Easter and following #EasterRailWorks on Twitter.