The men were working for concrete contractor Bell Formwork Services on Costain’s Frankley Water Treatment works contract in Birmingham.

Two steel fixers, a 65-year-old man from Walsall, and a 45-year-old from Staffordshire, had been raised nearly 5m above ground in separate scissor-lifts to take measurements of the tank wall.

They were preparing a concrete pour on the site where a massive new water tank was being built.

Birmingham Magistrates’ Court heard that shortly afterwards the wall of rebar collapsed, falling like a breaking wave, knocking over both scissor-lifts with the operators still inside.

The older steel fixer remained in his platform as it landed on its side and crashed into a nearby support frame. He suffered bruising and pain in his leg and shoulder.

His workmate was flung from his platform as it landed on its side against a nearby support frame. He suffered bruises to the head, legs and body.

One of the injured men had to be lifted free of the scene using the site crane

Three other workers on the ground managed to take cover and avoided injury.

An Health and Safety Executive investigation into the incident on 12 November 2012 found both Bell Formwork and Costain had failed to ensure the workers were able to do their job in safety.

HSE identified that the steel reinforcement for the tank walls, 21m long and 6.3m high, was unstable due to its size, the slenderness of the steel bars and the weight of the steel at a high level.

A temporary support should have been put in place at 7m intervals. However, on the day only two support frames were used at 8.3m spacing.

HSE found principal contractor Costain did not plan, manage or monitor the work properly. They were aware of the risks of collapse and the need for temporary support, including from a similar collapse in March of the same year at another site.

Despite this they did not apply their own temporary works management arrangements, which would have included a series of checks.

Bell Formwork Services failed to take reasonable steps to prevent the collapse of the wall and failed to identify that support was inadequate because there was no managerial level supervision or monitoring during these early stages of the work.

Both firms pleaded guilty to breaching safety regulations were each fined £15,000.

After the hearing, HSE inspector Luke Messenger said: “This was a serious incident and considering the size and weight of the wall, and the height from which the scissor-lifts overturned, it is extremely fortunate that no serious or even fatal injuries occurred.

“Both companies were experienced in their industry and should have done better.”