East Midlands Trains says its services are back to normal again after disruption caused by overhead wiring problems yesterday (Wednesday).
The issue, in the Radlett area, caused major disruption for commuters.
A spokesman for the firm said: “Following repair work carried out by Network Rail overnight, train services between London and Luton have resumed today and East Midlands Trains plans to run its regular timetable, although there are currently delays to peak services as a result of further engineering work being carried out by Network Rail this morning.
“We would like to apologise to passengers for the severe disruption to our services yesterday which was caused by a serious overhead wire problem.
“Network Rail engineers carried out repair work overnight to allow us to restore services this morning.”
East Midlands Trains tickets that were not used yesterday are also valid for use today.
Service information is available at www.eastmidlandstrains.co.uk or by following on Twitter at @EMTrains.