The carriage remained upright after the derailment

The first carriage of the Silverlink commuter train came off the tracks just south of Hemel Hempstead station in Hertfordshire at about 0920 GMT.

Nobody was hurt, but 35 people on board were led by staff along the track to the platform.

An emergency timetable was put in place for trains between London Euston, Milton Keynes and Northampton.

The train was the 0834 GMT Silverlink service from London Euston to Milton Keynes, and was travelling slowly at the time of the accident.

The carriage derailed - but remained upright - when its second and third set of wheels came off the track.

Two sets of wheels came off the track

A British Transport Police spokesman said: "Everybody was fine, as far as we know.

"The cause of the derailment is not yet known but a full investigation will be carried out.

"Her Majesty's Railway Inspectorate have been advised."

No other trains were involved in the incident.

The four lines along the route were closed after the accident, and buses were laid on between Watford and Tring to ensure commuters could continue their journey.

On Tuesday afternoon, a spokesman for Network Rail said that the train was being moved from the site and inspectors were at the scene.

Slow lines closed

He said the two fast lines, one in each direction, were reopened at 1020 GMT.

An emergency timetable was put in place, with four trains an hour running in each direction.

Two were calling at all stations between Euston and Milton Keynes, while another two were running semi-fast between Euston and Northampton.

Virgin Trains were running one train an hour northbound between Watford and the Midlands.

It is hoped the two slow lines will be opened by Wednesday morning, and services will return to normal.