The secret behind the Nazi U-Boats or Grey Wolves which nearly drove Britain to defeat in the Second World War is finally out, with a new book revealing the facts about their surrender to Scotland in 1945.

Written by David Hird, the book, The Grey Wolves of Eriboll, revealed the untold secret surrender of 33 German submarines in one of Scotland's most remote corners.

For 12 days from 10 May 1945, the U-boats sailed into the little-visited Loch Eriboll, near Cape Wrath. It was the biggest ever gathering of Nazi submarines, and it was top secret.

Hird, who spent two years tracking every single one of the submarines, learned from local gossip that the U-boats had come in to the loch.

"The crews were happy to surrender in Scotland. It was the Russians they were worried about. They just didn't want to give up to them," The Scotsman quoted Hird, as saying.

Hird believes equipment, including explosives, was simply hurled over the side of the vessels into the loch.

Surrendered submarines included U-1231, which was used as the U-boat pack's "off-licence" and was laden with wine.

Locals living near the 10-mile long Loch Eriboll were sworn to secrecy after the war.

Hird managed to speak to a few elderly people who remembered seeing the vessels, and also interviewed crew from British and Canadian ships who escorted some of the U-boats into the remote Scottish bay.

Eventually, the U-boats were all scuttled by the British. (ANI)