Overcrowding is expected on all rail services into London this morning because of a total loss of signalling power which means no services will be running into Victoria from East Croydon.
Govia Thameslink Railway is advising passengers NOT to travel with Thameslink, Southern or Gatwick Express from the south.
They say there is a very limited service running across the network.
A GTR spokesman said: “Network Rail is working hard to rectify this fault but in the meantime passengers are urged not to travel from the south on our remaining services which will be heavily overcrowded.”
Read more on the National Rail website.