Commuters can expect severe train delays following a cable fire and power cut at London Euston station.
The station has been evacuated and no trains are travelling in or out of Euston.
Southern services are suspended between Milton Keynes Central and Watford Junction.
National Rail said there will be disruptions until 8pm.
A statement from London Euston said: “No trains are running due to a line-side fire near South Hampstead that has damaged signalling equipment.
“Network Rail has engineers on site trying to restore services as soon as possible.”