Passengers across the entire South West Trains network could face delays today due to a 'system problem'.
The operator - which runs trains between Southampton Central and London Waterloo, as well as many other major Hampshire train stations - has said that it has suffered a "problem with the system that matches crew rosters to train timetables" at London Waterloo.
As a result this could affect all passengers heading to and from the capital, with delays of up to 20 minutes, cancellations or revisions until the end of the day.
South West Trains said the disruption is also expected to affect services tomorrow.
Passengers are being advised to check the information boards at stations before departure as trains are being altered at very short notice.
The operator apologised for the disruption.