The dive I believe helped shape King's care for the planet

FLOATING in blue silence beneath three metres of frozen Arctic Ocean, the young Prince of Wales was still for several minutes, transfixed by a cluster of ice stalactites teeming with tiny creatures.

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Prince Charles, then 26, had never seen anything quite like it or been so close to the raw power and fragile beauty of the natural world.

With the ever-present media pack and twitchy royal protection officers far away on the surface, the future King seemed lost in quiet revelation, said Dr Joe MacInnis, the Canadian diver who was down there with him 50 years ago.

He believes it was a profound moment that helped shape the monarch's lifelong concern for the planet.

Joe remembers: "He looked so intensely like he was trying to understand or absorb what he was seeing. I realised he was looking with three eyes - two in his head and one in his heart.

"It seemed like a very profound moment, as if he could already sense how fragile it all was."

Charles' historic visit to Canada's Northwest Passage - where he had that daring Arctic dive beneath the ice in 1975 - is now the focus of an upcoming ITV documentary in which explorer Steve Backshall retraces the royal's journey. Steve Backshall's Royal Arctic Challenge, which will be part of STV's Christmas schedule, promises to show the monarch as never before.

In it, he recalls the expedition and watches new footage from the same area now sadly transformed by climate change. Joe, 88, was an accomplished diver and explorer in 1975 when he was asked to take the young Prince then a Royal Navy helicopter pilot - on an Arctic dive.

Joe had already completed hundreds of high-risk dives beneath the ice and the previous year became the first scientist to dive under the North Pole.

But the prospect of being responsible for the safety of the future King filled him with a very different kind of fear.

"I was very concerned about what might unfold from a security point of view," said Joe. "I knew that the Scotland Yard officers and Royal Canadian Mounted Police were not divers and that as soon as I submerged with him I was completely responsible.