Tributes paid to British Olympic gold medallist sailor Andrew 'Bart' Simpson killed on America's Cup challenger Artemis in San Francisco Bay but how could he be trapped in capsized boat for 10 minutes?

Officials from the world’s most famous sailing competition are investigating how a British Olympic gold medal-winner came to be trapped underwater in his capsized boat for up to ten minutes, as team-mates and competitors alike tried to come to terms with the death of Andrew ‘Bart’ Simpson.

Questions have been asked not only about how his 72ft, 11-man catamaran came to capsize during its training session, but also more fundamentally about the safety risks of his “wing-powered” catamaran which was being used for the first time in the America’s Cup.

Simpson, who won a gold medal in the 2008 Beijing Olympics and silver during last year’s London Games, died while training on the Swedish vessel Artemis in San Francisco Bay.

His team said he was caught underwater by the AC72 catamaran’s platform for about 10 minutes before his body was recovered. Doctors both in the water and on the shore tried in vain to revive him.

The cause of Simpson’s death has yet to be established, however. All crews not only wear crash helmets and protective flotation padding but carry a small personal oxygen supply which gives about two minutes of air. So-called ‘nanny boats’ carrying medics and divers are always present, and a police boat was quickly on the scene.

His long-term friend and teammate Iain Percy said tonight: "Yesterday I lost my closest friend of over twenty five years, the friendliest and kindest man I have ever met. I cannot believe he is no longer with us.

"Now all our thoughts should be with his wife and two amazing boys who meant the world to him. Andrew has more friends than anyone and we will continue to support his family with all our hearts."

Stephen Barclay, chief executive of the America’s Cup Event Authority, said an investigation would address why the accident occurred.

“These boats are very fast and if these sorts of things happen then there are procedures and those sorts of things that we follow,” he told the BBC. “We have boats follow these vessels, there’s divers and doctors in case such things like this happen and those procedures were followed.”

Artemis Racing chief executive Paul Cayard said: “The entire Artemis Racing team is devastated by what happened. Our heartfelt condolences are with Andrew’s wife and family.”

The accident occurred two hours into a training session, with the wind speed thought to have been about 20 knots, more than sufficient speed to push such boats to their limits.

It is thought Simpson was serving as a race strategist for the boat, deciding on which direction to take and when to adopt aggressive or passive tactics. Sailors performing this role are usually positioned towards the back of the boat, though confirmed details of where he was and what he was doing at the time of the crash has yet to be released.

It remained unclear last night if the accident was a handling error while turning the boat downwind at high speed or during another manoeuvre, or if there was some sort of structural failure. Simpson had grown up racing against leading British Olympic sailor Ben Ainslie and was awarded an MBE in the 2009 New Year Honours list.

He lived in Sherborne in Dorset with his wife, Leah, and their two young children, but the family had temporarily moved to San Francisco so he could focus on training for the America’s Cup.