Two construction firms have been fined after a 6m metal beam fell from the sixth floor of a building, striking and injuring a worker on the third floor before crashing on to a busy street in the City of London.

The 32kg beam hit a 38-year-old building worker while he was on an access platform, breaking six of his ribs and fracturing three of his vertebrae. The man, a self-employed sub-contractor, was in hospital for a week and unable to work for two months.

He was working on the construction of the seven-storey South Place Hotel in Wilson Street, EC2, when the incident happened on 5 October 2011. McClaren Construction Ltd of Brentwood, Essex, was the principal contractor and John Doyle Construction Ltd, of Welwyn Garden City, which is now in liquidation, was a sub-contractor.

The Health & Safety Executive (HSE), which investigated, prosecuted both companies for safety breaches and both were sentenced at Southwark Crown Court on 10 December.

The court was told that several John Doyle workers were dismantling the temporary structural framework on the sixth floor of the building when they lost control of the six-metre beam. It fell down the side of the building and hit the worker, who was on a mobile work platform three storeys below. It continued to fall and landed in Wilson Street, a busy public highway on one side of the site.

HSE found that John Doyle Construction had failed to identify and implement reasonable control measures that should have been in place to prevent any beam from falling in that way. McClaren Construction approved its sub-contractor’s work method statement and also did not identify that controls were lacking.

In addition, neither company took any steps to make sure that no-one was working below the areas where the framework structure was being dismantled.

McClaren Construction Ltd, of Kings Road, Brentwood, Essex, was fined £22,500 with £14,854 in costs after admitting a breach of Section 3(1) of the Health & Safety at Work etc Act 1974.

The court indicated that had John Doyle Construction not been in liquidation, a £50,000 fine would have been imposed. However, John Doyle Construction Ltd, registered with Administrators at Temple Quay, Bristol, was fined a nominal £1 with no order for costs.

After the hearing, HSE Inspector Eileen Gascoigne said: “What happened at the building site that day had the potential to kill one or more workers and members of the public passing close by. It was entirely good fortune that the consequences were not even graver.

“The incident was entirely preventable. The risks were foreseeable and the measures that needed to be in place are well-known in the industry and were readily implemented afterwards.

“As an experienced principal contractor, McClaren failed to properly check the controls that John Doyle proposed for the work and failed to implement their own procedures for ensuring there was no risk to either other contractors or members of the public from the work taking place.

“John Doyle was also an experienced contractor and yet it, too, failed on an important safety issue.”

For safety information in the construction sector, visit www.hse.gov.uk/construction.