A 25-metre span of the roof, that was around six metres long and weighed two tonnes, was blown off its eight-metre high scaffolding end supports on 23 December 2012.

It struck the roof of an adjacent biomass shed before landing 50 metres away beyond the other end of the shed on a roadway used by delivery wagons and occasional pedestrians.

Fortunately the timing of the incident just before Christmas meant that the normally busy road was deserted.

Bedlington Magistrates’ Court heard that the roof structure was part of a temporary extension to a permanent shed at the power station, designed to increase capacity and provide weather protection during deliveries by tipper wagons.

In 2011 Pyeroy Ltd had been instructed by the owners of the power station to build a temporary extension to the biomass shed that was designed by an external scaffold design company.

This was dismantled in August 2011 once it was no longer required.

Then in May 2012, Pyeroy was asked to install another temporary extension, this time designed by its in-house design team. Although similar to the first structure, it was to be shorter and lower.

It was constructed in June and July 2012 by Pyeroy’s own workforce with the help of a specialist roofing contractor. But poor communication resulted in an incomplete design plan being used.

HSE established that although the structure was routinely inspected during the build and once it was brought into use from October 2012, it was inherently unsafe.

Magistrates were told that on 22 December it was noted that the weather was worse than normal, with the winds picking up. This meant some of the sheeting on the structure needed to be re-tied.

The temporary roof was blown off its end supports early the following morning. It ended up straddling a safety barrier and a dry riser pipeline between the main delivery access road and the legs of an adjacent conveyor.

HSE inspectors concluded that Pyeroy had failed to ensure those involved in the construction of the extension had the necessary knowledge and experience to do the work.

The company also failed to properly communicate with the build team and to check the construction was carried out as it should be.

Pyeroy of Gateshead, was fined £10,000 and ordered to pay £1.045.50 in costs after pleading guilty to safety breaches.

After the case, HSE inspector Andrew Woodhall said: “Thankfully no one was injured as a result of this incident, but it should not and need not have happened.

“It was easily preventable had Pyeroy Ltd ensured the work was carried out to the correct standards; that its team had the necessary skills and experience to carry out the work; and had it checked on the work during construction of the extension.

“Regardless of the wind speeds, no-one knew whether the structure would be properly built or had been properly built, so they could give no assurances about the robustness of the roof.

“As a result of these failings, workers and others visiting the power station were needlessly put at risk.”