Experts have been unable to explain why the scaffold boards on the gable end of a new house in Armthorpe flipped up and dislodged the ladder while 60-year-old Paul Grierson was standing on it.

Mr Grierson, the director of his own company Greenfield Northern Ltd, was about to fit fascia boards to the gable roof of the property on the Harden Mews development off Whiphill Lane last June when he fell 28ft to the ground.

He suffered serious pelvic and rib injuries which resulted in organ and respiratory failure two weeks later.

A jury at a Doncaster inquest returned a verdict of accidental death on Mr Grierson, who lived in Old Lane, Bramhope, Leeds.

Due to the interlude between the fall and his death, the Health and Safety Executive were unable to examine the scaffolding because it had been dismantled in the intervening period.

Mr Grierson’s son Ben, who worked as a labourer for his dad, witnessed the fall and said there were no previous problems with the scaffold tower.

Doncaster Deputy Coroner Fred Curtis said: “No-one was able to examine the scaffolding on that plot because no-one contemplated it would lead to Mr Grierson’s death.”

The ladder up to the scaffolding was not secured and did not have a block at the bottom but other people had used it that day and found nothing wrong.

Mr Grierson’s son, who was standing only 7ft away, saw the outer edge of the scaffold board flip up and two other boards also fall away. After being taken to hospital the injured man was never well enough to offer his own explanation of what had happened.

“There was no expert investigation on the day and it may well be there was a problem about which we shall never know. There could have been a problem with materials or human error or it may have been a completely freak incident which involved the board flipping up,” said Mr Curtis.