William Batten (66), trading as Bill Batten Concrete Cutting and Demolition Service, was injured when he removed key timber supports at the corners of the roof,  destabilising it and causing it to collapse on top of him.

The collapse was witnessed by schoolchildren in a nearby playground on their lunch break.

Batten suffered a fractured vertebrae and neck injury. He was hospitalised for a week but has since returned to work undertaking light duties.

An HSE investigation found Batten had started work he was not supposed to.

It identified that the roof of the temporary classroom had been supported by timber in each corner. Steel fixtures had been inserted to add additional structural support for the windows, but not the roof.

North and East Devon Magistrates’ heard that Batten’s firm had been contracted to demolish two buildings at Lympstone Church of England Primary School.

A ‘soft strip’ of the temporary classroom took place on 11 June 2013 and demolition of the main structure by mechanical means was to be carried out on the following days when Batten’s son, business partner and planner of the work, returned from leave.

A further risk assessment and method statement was to also be submitted prior to the structural demolition going ahead.

But after Mr Batten had finished the ‘soft strip’ with two labourers, he decided to undertake further stripping work, including the removal of the timber supports to the corners and cladding.

Batten wrongly assumed that steel stanchions supporting the windows were holding up the roof.

When the wooden struts to the corners of the building were removed, the roof became unstable and collapsed.

The two employees narrowly escaped harm but Batten, was trapped underneath the roof for several hours.

William Melvin Batten, trading as Bill Batten Concrete Cutting and Demolition Service, of Kingsteignton, Devon, was fined £500 and ordered to pay costs of £868.90 after pleading guilty to breaching CDM regulations.

Speaking after sentencing HSE inspector James Powell, said: “William Batten failed to ensure the demolition of the temporary classroom was carried out without presenting a danger to anyone, including himself and two employees.

“The work had been properly planned, by his son and partner, in advance and had the work been carried out in that manner, this incident would not have happened.”