This picture, taken by passenger Martin Stewart, shows the broken cable hanging over the track in Radlett station yesterday.
Severe delays have been predicted on Southeastern, East Midlands Trains and First Capital Connect until the end of the week.
More top news
Jodie Hills is calling for a boycott of a nightclub after she claims she was pushed onto railings outside. Contains graphic images.
A 3-year-old from Tower Hamlets is among hundreds of London kids identified as potential extremists.
The shipment was found by a worker as he unpacked bananas. Police say they are investigating.