Passengers suffered travel chaos when a damaged cable halted train services on the West Coast Main Line.
Services out of London Euston were cancelled and commuters were advised to use other operators while the fault was being repaired.
There was a complete loss of signalling after the incident was reported south of Milton Keynes early on Friday.
Dozens of trains were hit by the fault and services would not return to normal until later, Network Rail said.
The first train to leave Euston was the 0817 BST to Liverpool about two-and-a-half hours after the fault was reported.
Virgin Trains said services were returning to normal.