David Thomson, 22, was working as part of a Ness Engineering team removing the mast at the former RAF remote radar head at Unst, Shetland, on August 23 2010.

Thomson and his colleagues were working from inside the mast and were unbolting pieces of metal and wood and loading them into a telehandler with a bucket attachment, so that they could be safely lowered to the ground.

But one piece of metal was proving tricky to shift so the men decided to stand in the bucket attachment so that they could be lifted up and unbolt the metal from the outside.

They then balanced the piece of metal, which was about four metres long, on the bucket as it was lowered to the ground.

But when they were still nine feet off the ground the metal slipped, and a smaller piece of metal caught the back on Thomson’s boiler suit, catapulting him out of the bucket to the ground below.

He fractured a vertebrae in his back, broke his left arm in two places, broke his thumbs and received multiple abrasions to his face and neck.

An investigation by the Health and Safety Executive found that although Ness Engineering had carried out a risk assessment for the dismantling operation, it was not part of the planned system of work to use the bucket attachment on the telehandler, nor to access the mast from the outside.

After the hearing, HSE Inspector Alan MacKinnon said: “The bucket attachment on the telehandler was not suitable for transporting people and as soon as Ness Engineering allowed their employees to be lifted up in it, the risk assessment they had carried out became meaningless.

“It was entirely foreseeable that there was a risk of either the men or the metal falling from the bucket, yet the company did nothing to ensure they had the right equipment on site to allow Mr Thomson and his colleague to carry out their work safely.”

At Lerwick Sheriff Court yesterday Ness Engineering Ltd, of Stuartfield, Virkie, Shetland pleaded guilty to safety breaches and was fined £26,700.