Hundreds of commuters between Birmingham New Street and London Euston were delayed after a power cut caused signalling problems on trains.
A disruption in the power supply between Milton Keynes and Wolverhampton caused signals to go offline from 4pm today (Tuesday) and power was not restored until nearly 7pm.
A Network Rail spokesman said: “There was a loss of external power and services were initially suspended because overhead power could not get to signals.
“We were able to get people down on to the tracks to signal manually but it did affect rush hour traffic. Trains were able to get through but obviously there’s a loss of efficiency when you’re signalling manually rather than using automatic systems.
“There will have been some services cancelled because there’s a gap between the power going down and when we can get people out there to get the trains moving again, but we acted as quickly as possible.”