South Western services between Wimbledon and Surbiton are set to be majorly disrupted until 10pm due to a police incident.
Trains running between Wimbledon and Surbiton maybe be cancelled, delayed by up to 50 minutes or revised, National Rail said.
Earlier, Southern services were unable to run between Shepherds Bush and Watford Junction, adding 40 minutes to journey times.
Avanti West Coast and London Northwestern Railway trains were also been disrupted over the issue.
National Rail warned that a points failure near Willesden Junction was causing disruption to trains running between the stations, as well as to London Euston.
It warned that trains between Watford and East Croydon, or to Selhurst, may be affected, explaining that the route had been “blocked entirely”.
