Fresh disruption is expected at Waterloo, Britain's busiest railway station, on Bank Holiday Monday over a signalling problem.
Passengers have been warned there are likely to be "many cancellations" because of the points failure between Waterloo and Surbiton.
Engineers are working to fix the problem affecting South Western Railway services, which comes as major works at the station are due to come to an end.
A message on the National Rail website said: "Mainline trains that run through Surbiton are unable to access London Waterloo.
"These services will be heavily disrupted with many cancellations and we strongly advise that you check your journey before you travel."
Passengers coming in from locations including Windsor, Reading and Shepperton have been advised to expect delays too.
Waterloo station has been hit by chaotic scenes in recent weeks because of problems including signal and points failures, which affect the part of the track that can move, as well as a minor derailment.