On the night of the 4th August 1941 the crew of Kriegsmarine U-boat U-1066 under the command of Kapitänleutnant Reh-Geweihsprosse attempted a daring attack on the port of Liverpool. However, in an attempt to gain as much unaware shipping in the U-boat's sights as possible the navigator, Obersteuermann Unhorban made a catastrophic error which resulted in the boat entering the mouth of the Manchester Ship Canal. Unable to dive and bereft of any hope of escape the Commandant decided there was no alternative to surrender. However there was a precious cargo in the hold - the fabled Primrose and Blue Box. Determined that the Box should not fall into the hands of the Allies he gave his second in command, Leutnant zur See Hartshorn, the duty of leaving the boat unseen and hiding the Box in a secure location and contacting the homeland with coordinates for it's retrieval once the war was over.
The fate of the missing submariner and precious Blue Box is unknown, but documentation found on board U-1066 implied that Leutnant Hartshorn, although a fluent English speaker, was a poor swimmer and perhaps was not the best candidate for a night time mission on the Ship Canal to hide the revered artifact.
Other documents found on board the U-Boat implied possible Enigma transmissions received prior to the surrender of the vessel to the Home Guard. 