According to wiki...After World War II many strange happenings were reported to have taken place at Shingle Street, including a failed German invasion.
Since the civilian population had been evacuated in May 1940 there were no eyewitness reports, although official documents remained classified until questions in the House of Commons led to their early release in 1993.
These papers disclosed no German landing, but did reveal that the Lifeboat Inn has been used to test an uncharged chemical bomb devised by Porton Down. In fact rumours of a failed invasion on the South and East Coasts were commonplace in September 1940 and helped to boost morale. Author James Hayward has proposed that these rumours, which were widely reported in the American press, were a successful example of black propaganda with an aim of ensuring American co-operation and securing lend lease resources by showing that the United Kingdom was capable of successfully resisting the German Army.