Roger Pearce, 56, of Newcastle-under-Lyme, was installing the vehicle’s offside light and mirror arm at the firm’s Lakeside works in Rocester, Staffordshire, when the incident happened on 3 June 2013.

Staffordshire Magistrates’ Court heard that Pearce had to crouch down so could not be seen by a colleague testing the steering, resulting in him being crushed between a wheel and the bodywork.

He fractured ten ribs; damaged the bones at the base of his spine, and injured his bladder and kidney.

He was hospitalised for ten days and is still undergoing treatment. He has not been able to return to work.

A HSE investigation identified that, at the time of the incident, there was a designated area of the assembly track where hydraulic fluids were pumped into the machine and steering and other systems operated to force the fluids through the system.

HSE found the assembly sequence for the telescopic materials handler was changed, which led to the fitting of the front offside light and mirror arm being moved from a point when the hydraulics were not live, to a point when the hydraulics were live and functions such as steering were tested.

JC Bamford Excavators Ltd, of Rocester pleaded guilty to safety breaches and was fined £25,000 and ordered to pay £1,390 in costs.

After the hearing, HSE inspector David Brassington said: “This was a serious incident with Mr Pearce sustaining injuries from which he has yet to recover.

“It was also a preventable incident. JCB had allowed the introduction of a serious hazard and failed to assess the risk from this change. The controls that were in place were inadequate and Mr Pearce suffered serious harm as a result.

“Since the incident, the fitting of the light and mirror arm has been moved back to earlier in the assembly sequence when the hydraulics are not operational.

“Other changes have included barriers around the assembly area and the introduction of a banksman to control personnel working within it.

“The risks associated with the manufacturing processes involving large pieces of powered equipment should be assessed to ensure that there are effective controls and safe work procedures to protect those involved in this work.”