Serves to and from London Euston railway station were severely disrupted after a train derailed near Milton Keynes.
London Northwestern Rail said the "low speed" derailment happened in Bletchley near Milton Keynes on Thursday.
The railway operator said there were no passengers on the train and no injuries had been reported.
National Rail warned “major disruption is expected until the end of the day”.
“A train has derailed in the Milton Keynes Central area, closing some lines,” a statement on its website said. “Trains running through this station may be cancelled, delayed by up to 90 minutes or revised.”
Milton Keynes is on the West Coast mainline, connecting London to the Midlands and North of England and Scotland.
London Northwestern Railway and Avanti West Coast operate the trains on this line.
Several trains departing from London Euston were delayed by more than 90 minutes following the incident.
This includes Avanti West Coast trains to Manchester Piccadilly, Glasgow Central, Chester, Edinburgh and Liverpool Lime Street.
Disruption lasted until the end of the day, causing misery for thousands of commuters. At the end of Thursday trains arriving into London Euston were still cancelled and delayed into the early hours of Friday morning.
Avanti West Coast said people may instead use their ticket on the following services:
London Northwestern Railway said its customers can instead use their tickets on the following routes:
