Thousands of passengers faced travel chaos this morning after a train came off the tracks as it left a depot.
The derailment happened near Dorking, about 40 miles south of London, when the train was not in passenger service.
It sparked delays to Southern trains into London Victoria and South West Trains services into Waterloo.
A National Rail spokesman said: "An empty passenger train has derailed as it was leaving the depot at Dorking this morning resulting in disruption to journeys between Horsham and Leatherhead. This is expected to continue until 1pm."
Delayed passengers used Twitter to vent their frustrations.
The disruption comes at a bad time for Southern Railways, which has recently faced widespread criticism from passengers and politicians over poor performance.
The operator is also currently embroiled in a bitter industrial row with union RMT, which sparked a round of strike action last week.