Thousands of rail passengers travelling from London Euston face severe disruption after 1,000m of cables were damaged.
Services from the capital to the West Midlands, Manchester, Liverpool and Glasgow will be subject to delays and cancellations throughout Sunday.
People have been warned there will be no trains leaving Euston after 21:00 GMT as engineers are working overnight.
National Rail said the disruption would run into Monday morning.
It said the overhead electric wires at North Wembley junction were damaged on Saturday.
The disruption will affect Avanti West Coast, London Northwestern Railway, London Overground and Caledonian Sleeper services.
London Northwestern Railway said its services between London and the Midlands would be “severely limited” throughout Sunday.
“There is significant damage to overhead electric wires and this will affect Monday morning commuters too,” a spokesman said.
He said it had a ticket acceptance agreement with other train operators.
London Euston is the UK’s fifth busiest railway station.