The tragedy happened while Dr Graham Allwright, 48, was one of a party of 11 leisure divers at a diving school in Fort William in the West Highlands.

The accident happened in the dark in Loch Linnhe in December 2001.

Donald Mcgregor, managing director of Stenmar Engineering, which runs the Underwater Centre for the oil and fish farm industry, said the death was a mystery.

He said there was no obvious explanation as to why Dr Allwright suddenly descended to the seabed just as a safety boat was about to reach him.

Passed exams

The doctor, from Formby and his diving buddy came to the surface and signalled for help because one of their torches was not working.

The father of two teenagers was recovered unconscious 10 metres under the surface but efforts to resuscitate him failed.

On Wednesday a fatal accident inquiry was ordered. It will be held at Fort William Sheriff Court on 20 and 21 February.

Dr Allwright's wife Jane, 47, said that her husband had become interested in scuba diving about a year earlier, and had passed all the necessary exams.

The Fort William trip with 10 other qualified divers was the doctor's first sea and night-time dive.