In the latest in a series of problems, commuters reported as many as seven trains backing up behind one another as engineers tried to fix the power supply at Bletchley yesterday.

Northampton Rail Users' Group treasurer, Shaun Hope, said the line had previously failed just 10 days earlier and journeys to London had been severely delayed.

He said: "People told us it was taking them two-and-a-half hours to get to Euston which, when you're commuting to the office, is not a good start to the day to say the least.

"Of course upgrade work and maintenance needs to be carried out, and as long as people know their journey will be affected they can plan around it, but these sorts of failures make journeys very difficult. It's made worse when planned work overruns, which has happened several times."

Yesterday's disruption comes ahead of major West Coast engineering work this weekend, which will mean there will be no direct Virgin Trains services to and from Euston on Saturday and Sunday.

Chair of the Rail Users' Group Sally Keeble, Labour MP for Northampton North, who was caught up in the chaos, said she was "absolutely appalled" at the failure.

She said: "I heard people being told they could come back and use their tickets the day after, which is just ridiculous. If you say that to someone who has an urgent business meeting, they will look at you like you're from another planet.

"After all the money that has been spent upgrading and improving the system, it is horrifying that it is still so fragile."

A spokesman for Network Rail said the power supply to the signalling system failed at 8.35am in the Bletchley area on the West Coast Main Line, with all trains re-routed or cancelled.

Trains from the north were turned around at Rugby and trains from Euston station in London could only get as far north as Northampton, with buses being used between Rugby and Northampton. Normal power was restored at 11am.