Commuters faced fresh rush hour problems in south-west London after a lorry hit a bridge.
Southern rail services between Clapham Junction and Victoria were affected after the collision at Battersea Park.
The operator said the disruption would continue until at least 10am.
Some services could be cancelled as a result. Engineers from Network Rail are travelling to the bridge to inspect the damage.
Southern confirmed a lorry struck the bridge at around 8.20am.
Southern said tickets are being accepted on the Tube, Thameslink and Gatwick Express services for passengers looking to make alternative journeys.
Some passengers have taken to Twitter to vent their frustration at the delay.
In a sarcastic tweet, Vanessa Furey posted: “Was starting to get nostalgic that It'd been ages since my train was ridiculously delayed. Thankfully Southern have fixed that for me.”
It comes after commuters complained of a night of carnage on London's railways when Southeastern services struggled to recover from an electrical fault which damaged part of the line near New Cross.
As tempers flared a City worker allegedly punched a guard in front of stunned commuters on a platform at Cannon Street station.
Southeastern said the bridge strike had also affected trains between London and Chatham.
The operator was further plagued by a separate bridge strike in the Orpington areas, which caused delays in both directions.
