The Health and Safety Executive investigated Kent Commercial Finishings Ltd and LCS Interiors Ltd after the incident on 14 July at a development at Wilton Plaza in Westminster.

Labourer Sean Forsythe, 22, from Streatham in London, was cleaning a screed pump, which is used to move concrete from a mixer to the floor of a building.

City of London Magistrates’ Court heard that the hose he was using to clean the pump got caught in the rotating blades of the mixer, pulling his hand into the machine.

Forsythe suffered severe cuts to his right hand, leaving him with permanent damage.

The investigation by HSE found the screed pump had no safety grill to stop the blades when it was lifted.

Magistrates heard a few months earlier another grille had broken off a pump but was not replaced– despite a written procedure being in place.

HSE prosecuted Kent Commercial Finishings Ltd of Monkhurst House, Sandy Cross, Heathfield, East Sussex – who were the contractor who hired the screed pump.

The company pleaded guilty to breaching Regulation 11 of the Provision and Use of work Equipment Regulations 1998, and was fined £3,000.00 and ordered to pay costs of £2,000.00 at an earlier sentencing.

LCS Interiors Ltd of Little Burrow, Welwyn Garden City was responsible for the weekly inspection of the plant and machinery and was also prosecuted.

The company was found guilty of breaching Regulation 11 of the Provision and Use of work Equipment Regulations 1998 and was fined a total of £10,000 and ordered to pay costs of £30,000.

Following the hearing, HSE Inspector, Monica Babb said: “Mr Forsythe has been left with long term damage to his right hand – because a safety grille was not in place, a completely avoidable incident.

“It is simply not acceptable the companies involved in this incident failed to take action when a crucial piece of safety equipment broke.

“Had staff been adequately supervised and if the equipment had been properly maintained, this incident would not have happened.”