Devon Stoner, 44, of Whitehorse Road in Croydon was prosecuted after the incident last January when he was carrying out demolition work for Sloane Demolition Limited in Kent.

Maidstone Magistrates’ Court heard that on 20 January 2011, five employees, including the defendant were sorting through rubble and reclaiming bricks at the former Leybourne Grange Hospital in West Malling, Kent.

The two-storey building was being demolished with the use of a 13 tonne, 360 degree excavator.

Workers were putting bricks from a demolished chimney breast into the bucket of the excavator which the operator had left switched off but with the keys left in it.

Stoner climbed into the excavator and began to move it around the site.

But he was unable to control the machine and caused a wall to collapse.

His co-worker was unable to move out of the way quickly enough and was trapped. He suffered serious injuries to his left leg, a broken right ankle and a shattered shin. He has had to have a steel plate inserted into his right shin and ankle.

Stoner was not trained or authorised by Sloane Demolition Ltd to operate this type of equipment and therefore should not have been driving the machine on the day of the incident.

HSE Inspector David Fussell said: “Workplace transport is the second biggest cause of fatal accidents, and it is extremely fortunate that this incident didn’t result in a death.

“The HSE will not tolerate employees exposing their colleagues or members of the public to unacceptable risks due to their work practices. There is simply no excuse for employees to plead ignorance of good health and safety practice.”

Stoner pleaded guilty to breaching section 7(a) of the Health and Safety at Work etc Act 1974. He was ordered to undertake 120 hours community service and pay £500 in costs.