The Halifax bomber was struck by heavy flak and made a successful crash landing 600ft down a water inlet in northern Norway.

The sunken bomber will be protected as a war grave because of the likelihood of the remains of the two airman still being on board. Four of the six-man crew bailed out into a dingy but nothing was ever seen of navigator, Flight Sergeant Albert Columbine, or wireless operator, Arthur Evans. It is believed they drowned when the bomber went down.

The bomber was part of 35 Squadron and took off from RAF Kinloss on April 28, 1942, to find and sink the Tirpitz, which was the heaviest ship in the world at the time.

Professor Martin Ludvigsen, of the marine technology department at the Norwegian University of Science and Technology, said: "It was a construction company which found the plane initially.

"They didn't realise it was there or what it was. We went to the site and used a remote controlled underwater vehicle which dived to 180 metres.

"It was quite exciting. We could see from the images that it was the Halifax and was in good condition.