Commuters are facing a day of chaos on the rail network after the troubled West Coast Main Line between Birmingham and London ground to a halt.

Overhead power lines came crashing down in Hertfordshire on Monday lunchtime, leaving passengers stranded on a Virgin Trains service for about four hours.

Engineers took until 9am today (Tuesday) to mend the fault near Berkhamsted and it was not until noon that trains were running as normal between New Street and London Euston.

The fault meant misery for passengers heading for the capital as they were forced to cram on to reduced services or take alternative routes.

A spokesman for Network Rail said an investigation was underway to determine whether the problems were caused by faulty wiring or a defective Virgin Pendolino train.

In January 2009, the West Coast Mainline was crippled by five separate overhead power line failures over seven days despite an £8 billion upgrade to the network.

Virgin Trains public affairs manager Alan McLean said: “We share the frustration of our passengers. This should be one of the best train services in the world so it’s disappointing that it is disrupted.

“We are working at the very highest level with Network Rail to make sure it doesn’t happen again.”

Services were suspended after the problem was reported but a small number of trains were able to run on a reduced service for commuters on Monday night after two of the four tracks were opened.

No trains ran between Birmingham and Euston until 8am on Tuesday and only two out of three hourly trains were running until lunchtime.

Chiltern Trains were accepting Virgin tickets between Snow Hill and Marylebone and Cross Country Trains were accepting tickets for passengers to link to the Great Western Service between Reading and Paddington.

Network Rail spokesman Keith Lumley said: “We are trying to find out whether it was a fault with the train or the power lines.

“Unfortunately these things do happen from time to time.”