One of the workers, a 60-year-old from Barnet who does not want to be named, broke a bone just below his knee and suffered extensive tissue damage to his foot and ankle.

Westminster Magistrates’ Court heard that the injured workers were part of a team preparing a mini-digger for shipment to Australia in December 2012.

During the final machine clean the digger was inadvertently put into reverse and struck an employee.

In trying to release him, the vehicle was again reversed, causing him additional injuries and injuring another worker.

A third had a lucky escape because he was under the vehicle at the time, but managed to move away just in time.

The court was told that One Call workers devised their own system of work that was inherently unsafe, and that none of them had received any formal training.

One Call Hire Ltd, of Crown Road, Enfield, was fined £4,000 and ordered to pay £1,036 in costs after pleading guilty to a single breach of the Health and Safety at Work Act.

HSE Inspector Chris Tilley said: “It is clear that there was no safe system of work in place for work in and around the digger, either of a formal or informal nature.

“Had the work been properly assessed, and measures taken to isolate power to the engine and make it safe, then the two workers could have avoided injury.

“One Call Hire Ltd has accepted its failings in this regard, and we hope this prosecution sends a clear message to others.”