Colin Dickson, 38, of Motherwell, Lanarkshire, died when the temporary suspension points on a suspended beam he was under failed at the Lakeside Energy from Waste installation in Colnbrook.

The 1.4 tonne beam fell five metres onto Dickson causing fatal injuries to his chest, and fractures to his legs and back.

His employers J H Carruthers Ltd and one of its supervisors, John Hamilton, have been prosecuted after an investigation into how the lifting operation failed.

Maidenhead Magistrates’ Court heard on 29 August 2007, a team of five people were installing two cranes in the hall of a new incinerator building.

They were lifting two steel beams to a height of approximately 18 metres, which then had to be welded to the underside of the roof beams that were fixed to the rafters.

HSE Inspector Karen Morris said: “This was a complex and unusual lift which went drastically wrong due to a lack of competent planning and a failure to supervise and carry out the task safely.

“The risks involved in such lifting operations should not be underestimated.

J H Carruthers Ltd (formerly Konecranes (UK) Ltd), of Peel Park Place, College Milton, East Kilbride, pleaded guilty to safety breaches and was fined £180,000 and ordered to pay costs of £74,000.

John Hamilton, of Strathaven, Lanarkshire, pleaded guilty to breaching lifting regulations and was fined £1,500 and ordered to pay costs of £400.