Rush-hour commuters faced widespread travel disruption last night after lightning struck an electrical substation, causing many trains to be cancelled.
Services in and out of London's Victoria station were the worst affected. The lightning strike at south Wandsworth, near the central London transport hub, caused a fire that badly damaged the substation, leading to a power failure and serious signalling problems.
A National Rail spokesman said the lightning hit at 5.30pm yesterday - just as many people would have been leaving work to make the journey home.
Engineers worked throughout the night to fix the "serious problem", with commuters travelling into London from the South East facing minor disruption on some routes this morning.
Rail company Southeastern bore the brunt of the signalling failure, with no services running in or out of London Victoria yesterday evening.
There were some services on other routes from London out towards Kent and Sussex, however.
Southeastern said passengers were transported on alternative high speed routes, on London Underground or Southern railway trains or buses, until the problem was fixed.
Southern Railway was also affected, with services between Battersea Park and London Bridge suspended.
South West Trains told passengers there were delays of up to 40 minutes on services to and from London Waterloo because of the signalling problems.