A broken rail in the Finsbury Park area is expected to disrupt trains to and from London until the end of the day.
National Rail is warning that services between Stevenage and London Kings Cross/Moorgate may be cancelled or delayed by up to 15 minutes.
Thameslink, Lumo and LNER are among the operators affected by the problem.
Meanwhile a road outside Victoria Station remained blocked and buses were on diversion on Tuesday evening, after an elderly man was hit by a bus on Tuesday afternoon.
The man was taken to a central London hospital following the crash. His condition has not yet been confirmed.
Earlier problems on the Elizabeth line that saw major disruption after a power outage have now cleared, according to TfL.
