Network Rail investigators are still unravelling the chain of events which led to the sleeper being forgotten by the maintenance crew on Tuesday, August 9, but vandalism has been ruled out.

The London-bound train was travelling at 100mph at around 6am when it hit the 200lb wooden sleeper lying across the track, catapulting it into the air.

Disaster was narrowly averted by the the quick-thinking of the driver who spotted the obstruction and slowed the train before the impact.

The driver, who has been praised by Network Rail, then got out and averted the danger of a second collision by clearing the sleeper from the downline where it landed.

Accident investigators launched a probe and quizzed a six-man maintenance crew who were working in the area the previous night.

Network Rail spokeswoman Laura Dobson said: "The investigation is on-going. But it has been discovered that it was not left there as an act of vandalism, it would have been as a result of the overnight engineering work on the track.

"Obviously there would have been one person on site responsible for saying that the area was safe and they have been suspended. They will be retrained and brought back. They are not a Network Rail employee but a contractor.

"Safety at Network Rail is the priority and there will be recommendations which come out of the investigation which will be put in place to ensure this does not happen again."