Train passengers travelling between Sheffield and London have been warned to expect disruption today because of signalling problems.
A fault at Harpenden, between Luton and London St Pancras, has led to cancellations and delays on the London St Pancras-Nottingham-Sheffield route.
Network Rail, which owns and maintains the railway infrastructure, had engineers working through the night to repair the fault.
It is hoped services will operating as normal by midday.
An East Midlands Trains spokesman said: "We are looking at running a limited train service on our Sheffield-Nottingham-London route. At present we are advising customers to keep checking regularly for further travel advice.
"In order to get you to where you need to be, we have arranged alternative routes. These routes remain the most comfortable and quickest journey options.
"If you are travelling to London from Sheffield you should use alternative services to Doncaster and connect with Virgin Trains East Coast services to London Kings Cross.
"If you are travelling from Chesterfield you should follow the guidance above and use Cross Country services between Chesterfield and Sheffield.
"All of the alternative routes are also available if you are travelling in the opposite direction. Don’t worry, we have already arranged for your ticket to be accepted by the other train operators.
"If you decide not to travel you can apply for a refund."