Passengers travelling on the Southern service are being warned to expect cancellations, diversions and delays because of a points failure that happened between Selhurst and London Bridge.
Staff say that they were informed that the train tracks - which allow the trains to move from one line to another, had failed between Streatham Common and Streatham at 07:09am.
Network Rail sent engineers out to fix the problem and work on the tracks began at 07:57am.
Services are resuming however disruption is expected via Crystal Palace until 09:00am.
All other lines between Selhurst and London Bridge have also been reopened.
Commuters using the Southern Service or travelling between Streatham, Streatham Common and Crystal Palace are advised to check before they travel.
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