Garry Leaburn, 25, and Derek Taylor, 19, both from Dundee, were killed when a five-tonne concrete slab fell on them as they carried out a major engineering job on the Orkney island of North Ronaldsay in 1997.

Procurator-Fiscal Graeme Napier said the two men were "not competent" to perform the work.

The trust pleaded guilty to breaching the Health and Safety at Work Act.

'No risk assessment'

The men travelled with the trust to the island to help repair a dry stone wall, but switched to repairing a concrete sea wall which had been damaged during a storm.

They were working in a hole below the wall on 6 August 1997 when it collapsed.

Despite a seven-hour rescue attempt, both men died from "traumatic asphyxia"

Mr Napier told the court that even a basic risk assessment would have revealed that the men were in danger.

"As a result of the failures to comply with their obligations under the Health and Safety at Work Act, two young men tragically lost their lives in North Ronaldsay," he said.

"Risk assessment is not a one-off but a continuing responsibility.

'Fun challenge'

"They had become involved in a major structural engineering operation without the competence needed. They should not have been involved."

The Health and Safety Executive, Orkney Islands Council and Scottish Enterprise all confirmed that the work on the sea wall was beyond the competence of the volunteers.

The trust became involved on the island after Prince Charles took a direct interest in the plight of the islanders who have insufficient manpower to repair frequent storm damage.

The 12-week course on North Ronaldsay was described as "fun, free and a challenge" and gave those who completed it a certificate signed by the Prince of Wales.

Two other organisations involved in the course were also fined.

Adult Community Training (Dundee) Limited pleaded guilty to failing to ensure the health and safety of the team and exposing it to risks.

The board of management of Angus College admitted providing inadequate information and training and failing to carry out proper technical or risk assessment.

Complete review

Solicitor David Stewart, defending the trust, said the organisation had no idea the men had switched to repairing the sea wall and expressed condolences to their family members.

The trust, under the motto "Helping young people to succeed", provides training, grants and support for business start-ups under the patronage of Prince Charles.

Up to 8,000 young people took part in more than 200 programmes in 1997-98.

It was the first serious accident in the history of the organisation, which was established by the Prince in 1976.