WW2 In Orkney - Barriers and POWs

The Orkney islands off the top of Scotland form almost a ring around Scapa Flow a piece of water that was used by the British Navy as a deep water achorage in both wars and held the intered German Imperial fleet at the end of WWI. It was in the 2nd world war however when one of its greatest tragedies occurred. On October 14th 1939 - HMS Royal Oak was at anchor with a crew of 1234 men and boys (teenage sailors in training) when U Boat U-47 was able to penetrate the defences and get into Scapa Flow. There she unleashed torpedoes, an action resulting in the death of 834 men. I may do a full blog on the story of the 'Bull of Scapa Flow' commander of U-47 and how she was able to negate the British defences at some point, but for now, the story is well documented elsewhere. That's the context, but prior to that attack the British were well aware of the risk posed by the various entrances to the flow, especially on the Eastern side that faced out to the North sea. In 1938 surveys had show…