William Laurie, 58, plunged 40 feet while working in Brighouse for his company, BJ Duct, of Newcastle.

The firm was carrying out contract work at Heritage Ceramics, Brighouse, in April last year.

Mr Laurie – a partner in BJ Duct – was moving ducts and repairing the roof.

David Stewart, of the Health and Safety Executive, said a colleague's report found better roof access could have been gained.

Mr Stewart said a stair tower rather than a ladder should have been used and a walkway erected, along with safety netting below the roof.

"The accident could have been prevented," he said.

Mr Stewart added: "A method statement did not go into enough detail into how the work was to be carried out."

Gareth Thomas was working with Mr Laurie on the asbestos/concrete sheet roof.

He was patching up roof areas being marked off by Mr Laurie, of Newcastle.

"I felt the roof thud," he said.

"I moved up to the apex and saw the skylight had a hole in it and that's when I saw Billy lying on the shop floor."

Factory supervisor Steven Brannan said he heard an almighty crack.

"It was like a shadow coming through the roof. I saw it hit the floor, ran across and saw it was Billy."

Consultant pathologist Dr Alan Padwell said Mr Laurie suffered fractured ribs and severe skull fractures after falling on to the concrete floor and would have been unconscious immediately.

Assistant deputy coroner Paul Marks said a number of deficiencies contrary to working at height regulations had been identified and the Bradford jury returned a verdict of misadventure.