Thameslink services are being severely disrupted at Blackfriars.
A Network Rail spokesman said: “Network Rail engineers are working hard to fix an electrical problem at Blackfriars station. We have had to turn the power off and stop trains running through the whole station, which means trains are being seriously disrupted.
“Thameslink services are having to finish their journeys at St Pancras International in the North and Elephant and Castle in the South.
“We are really sorry for the disruption this is causing to people’s journeys today and we are doing everything we can to get the railway back into use.”