Thomas Whitmarsh, 21, of Batley in West Yorkshire, was employed by a roofing contractor working for main contractor Watkin Jones & Son Ltd on the roof of the Menai centre on May 29 2007.

He fell nearly six metres through an unguarded opening in the roof to the floor below, sustaining serious head injuries.

Whitmarsh  spent several months in hospital and was making a gradual recovery.

But his brain injury exposed him to a much higher degree of infection and he contracted acute meningitis and died on 17 December 2009.

Evidence presented to Mold Crown Court included a pathologist’s findings which suggested that there was more than an 80% chance that the injuries from the fall contributed to his death.

The court heard that edge protection around the opening in the roof had been removed prior to the incident, and the company had failed to provide an alternative means to protect against falls.

Watkin Jones, which is based at Llandygai Industrial Estate in Bangor, was found guilty of safety breaches and was fined £450,000 and ordered to pay £98,000 in costs.

Following the hearing, HSE inspector Chris Wilcox said: “Poor co-ordination between the principal and the roofing contractors on this particular part of the site led to the edge protection being removed from around the roof opening without alternative safeguards in place.

“Falls from height are an alarmingly common cause of death and serious injury in construction. All too often straightforward practical precautions are not considered and workers are put needlessly at risk. Poor management of risk in this industry is unacceptable and HSE will take strong action when necessary.

“This tragic case should remind all contractors that work at height must be managed effectively and adequate safeguards should be in place to prevent falls.”