The worker, now 41, fell while removing tarpaulin from the one-storey roof extension at a flat in Collamore Avenue, South West London on 18 December 2006.

The Old Bailey heard James Thompson, who traded as James Thompson Carpentry and Building, was supervising the work on site.

However, a Health and Safety Executive (HSE) found Thompson could have undertaken a number of measures to have prevented the incident, but failed.

The tarpaulin had been put in place to provide the ground floor of the flat with weather protection. The worker was removing this when the tarpaulin snagged.

The man stepped on some insulating board that had been laid across the skylight, which gave way under his weight. He fell over three metres to the concrete floor below.

James Thompson, of Onslow Gardens, Wallington, Surrey pleaded guilty to breaching Regulation 6 (3) of the Work at Height Regulations 2005. He was fined £10,000 and ordered to pay costs of £7,000.

The injured worker suffered a broken back as a result of the fall and can now only walk short distances and needs to use a walking stick.

His condition will not improve, and the former judo fighter and rugby player will not be able to return to work in the construction industry again.

Speaking after the sentence, the injured man said: “Prior to the incident, I had an active life and enjoyed numerous outdoor activities, which I can no longer pursue.

“I no longer work as a result of my injuries. The incident has effectively turned my life upside down. I suffer terrible flashbacks and am currently on medication.”

HSE Inspector Ian Seabrook said: “The impact on this man’s life has been immeasurable.

“This incident could easily have been avoided, and illustrates there is no room for complacency even when working on small sites.

“Work at height is the single largest safety hazard on construction sites and needs to be properly managed.”