Three different train lines have been disrupted because of damage to the overhead electric wires between Shepherd’s Bush and Watford Junction.
Trains running between these stations may be cancelled, delayed or terminated and started back from Shepherd's Bush.
The operators affected are Avanti West Coast, London Northwestern Railway and Southern, with disruption expected until the end of the day.
It comes after emergency services had to respond to reports a person had been struck by a train between Kingston and Teddington.
The incident meant all lines in the area had to be closed, as power had to be shut to allow emergency workers access to the railway, but these have now re-opened and South Western Railway trains are now running as normal.
Meanwhile, there was significant congestion to traffic in central London, with at least one major road closed, after multiple horses bolted through Aldwych.
This has now cleared up, with traffic monitoring site Inrix no longer reporting any resulting congestion.
