Coastguards have called off their search for geologist Keith Cox who is presumed drowned after a boating accident in Scotland.

The father-of-three was swept overboard from his dinghy off the Isle of Mull. His wife Gillian, 59, made a heroic effort to raise help for her drowning husband, swimming for half an hour and then scaling a 100ft cliff.

The couple had spent three hours clinging to the hull of their dinghy after capsizing. They decided to swim to the shore as hopes of rescue faded.

Dr Cox, 65, of Bagley Wood Road, Kennington, was not wearing a life jacket and Mrs Cox tried to tow him to safety.

Oban Coastguard Watch Manager Charlie Charlton said: "Apparently he just went limp on her. He just slipped away."

Mrs Cox climbed about half way up the cliffs where she was spotted by some people in a yacht who raised the alarm.

The craft was found 90 minutes later with its sails in the water just off the coastline - but there was no sign of Dr Cox. The coastguard ordered a rescue helicopter from Prestwick and a lifeboat from nearby Oban to search the waters around the crash scene. Mr Charlton said: "For her age it's fairly incredible that she survived. She must be one tough lady. And of course, she must have been in shock too. It was quite a feat." Rab Taylor, of the Oban Coastguard, said: "The temperature of the water at this time of year is about 10M-<C and we must find this man if he is to have a chance of survival. This seems to be a tragic accident."

Rescuers have searched the shoreline for Dr Cox. A helicopter fitted with infra-red search equipment was even called in to scan the seas. Two local charter boats were drafted in as the rescue was stepped up.

But Malcolm Murray, of Oban Coastguard, said today: "The police divers are going to do another dive in the area today and a police helicopter will carry out an air search but as far as coastguards are concerned we've called off the search."

He said the cause of the accident was still unknown. There was nothing wrong with the boat and the weather conditions were not rough, he said.

He added: "One of the major contributing factors was that they only had one life jacket between them. It really was major contribution to his demise." Dr Cox's eldest son James was on holiday with him on the island but was not on the dinghy when it capsized. Dr Cox has two other grown-up children - William, who lives in London, and Emma, a teacher in Wales.

Mrs Cox, who is also a teacher, based in Abingdon, was today recovering in hospital in Oban. She swallowed sea water and injured her hand swimming to safety and was last night in a serious but stable condition. She is being comforted by friends and family.

In an interview with police, Mrs Cox said her husband appeared to have had a heart-attack as she tried to save him.

Dr Cox is a fellow at Jesus College, Oxford, and a world-renowned authority on volcanic rocks. Academics from across the world have visited him in the past to hear his views. He was due to retire next month.

The couple had left their home in Kennington last Sunday to visit the Edinburgh Festival before holidaying in a rented cottage on Mull. Long-time Oxford colleague Prof Stephen Moorbath, also of Bagley Wood Road, said: "I have never heard of him sailing before and we have been friends for countless years.

"He is a great character. He is cheerful, outgoing and full of wit and humour." He has many friends all around the world." He is quite distinguished."

Dr Cox was elected a Fellow of the Royal Society in 1988 to mark his contribution to science and he has continued his studies to the present day. He loved to visit Scotland with his wife.

Constable Alan Daujenis, of Mull Police Station, said there had been three boating fatalities off the island during the past 18 months.

The procurator fiscal - the Scottish equivalent of a coroner - will now have to decide whether to hold an investigation.

Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.