In the early hours of Saturday, October 14th, 1939, just after the outbreak of the War, the Royal Navy suffered a stunning loss. The battleship Royal Oak, stationed inside the main base of the Home Fleet at Scapa Flow, was shaken by a number of explosions. She became a furnace, rolled over and within minutes, had gone to the bottom, with nearly 800 men trapped inside. This daring feat of arms was eagerly seized upon by the Nazi propaganda service and they acclaimed Lieutenant Prien of U-47 as their first hero of the War. Hero because he had penetrated the defenses of ‘Impregnable Scapa’, where every previous attempt had failed.