Passengers at the country’s busiest railway station have suffered travel chaos because of a series of signal failures and other problems.
South West Trains services to and from London Waterloo were disrupted, delayed or cancelled.
In a message to rail users on Wednesday evening, the company said: "After a number of major incidents across our network today we are currently experiencing delays of around 60 minutes on most routes.
"Due to the severe disruption trains may be cancelled, altered or revised at short notice. Some services may also be diverted via an alternative route or terminated and started back from different locations.
"Also because of this disruption today crews and train stock has been displaced which may affect our service further.
"Over the course of today we have suffered multiple signal failures and a track defect at London Waterloo and a signal failure between Romsey and Eastleigh.
"A road traffic incident at a level crossing caused all lines between Staines and Egham to be blocked, additionally a freight train failed at Micheldever."
Stagecoach, which has run the SWT franchise since privatisation, has lost the contract and will be replaced by another operator from next month.
A fault with the signalling system also caused disruption at London's Paddington station, which was expected to continue until later this evening.
A spokesman for Network Rail said: "We're sorry that a track and signalling issue has resulted in disruption to passengers travelling to and from Waterloo today.
"This disruption was compounded this evening when a road vehicle struck and demolished barriers at a level crossing before the driver left the scene of the incident. This separate incident is under investigation by the police."