National Day of Prayer

In May, 1940, the Germans launched their attack against Holland and Belgium. The small British Expeditionary Force was trapped in France. The Germans advanced quickly in a pincer movement towards the British, who were pushed towards Dunkirk, the only port which was then left to them for evacuation. A huge number of men waited on the coast. Winston Churchill made a speech in the House of Commons in which he stressed the gravity of the situation. King George called for a national day of prayer and this took place on May 26th. Shortly afterwards' in spite of encirclement and aerial bombardment, 335,000 men were evacuated from Dunkirk.

Episode: The White Feather


Navarino

As far as I can discover, a fictional ship at the time the story is set - 1942. There was an HMS Navarino but it wasn't launched until 1945.

Link: HMS Navarino in Naval History of World Wars
Episode: Bad Blood


Norway

The Invasion of Norway, April 9 to May 9, 1940

Link: Weserubung
Episode: The German Woman, The White Feather