A power failure on the East Coast Mainline has been causing major disruption across the network.
National Rail said the supply failed at 17:37 GMT between Newark North Gate and Retford, affecting trains travelling between Peterborough and Doncaster.
Network Rail said staff were trying to rectify the fault and rescue passenger trains that had become trapped.
All services are due to run on Thursday but are expected to be busy and with some alterations, a spokesman said.
Many services, including to and from London, were cancelled on Wednesday night due to the ongoing disruption.
London North Eastern Railway apologised for the delays and advised passengers not to attempt to travel on Wednesday unless it was absolutely necessary.
Tickets for travel on Wednesday would be valid for Thursday, or customers could apply for a full refund for unused tickets, the firm said.
National Rail advised passengers to check their journeys before travelling.
A spokesperson said engineers were on the site and would be "working hard through the night to restore a full service for passengers" on Thursday.
"We understand the inconvenience this incident has caused customers and apologise for the disruption to their journeys," the spokesperson added.