Thousands of rail passengers had their journeys delayed after all lines were blocked in and out of Euston Station. The severe disruption was caused by a fault with the signalling system. Pictures on social media showed huge crowds gathered inside the train station after services ground to a halt.
Problems were first reported around 4pm on Thursday and National Rail warned passengers of "major disruption" after all services in and out were stopped.
Lines were said to be reopened about an hour later but delays continued well beyond 9pm.
Among those affected were passengers hoping to use Virgin Trains services on Thursday.
The company was advising customers to travel on Friday if possible - their tickets will still be valid.