Walter Simon was a World War II German spy. He successfully completed three missions in England. In 1939 he was arrested by MI5, spent three months in prison, then deported. In June 1940 he landed by U-boat in neutral Ireland on a naval intelligence mission but was captured that same day and sentenced to three years in jail. With the Battle of Britain about to begin following the fall of France, the arrival of a German spy on the Dingle Peninsula in June 1940 sparked enormous security concerns both in Ireland and the United Kingdom.