BBC South East's Robin Gibson takes a tour around the tunnels under Dover Castle, the centre for Operation Dynamo.
At 18:57 hours on 26 May 1940, the signal was received to start Operation Dynamo.
The evacuation of the British Expeditionary Force and French troops from Dunkirk's beaches on the north coast of France was about to begin.
With the British and French armies cornered by the advancing German army near Dunkirk in 1940, Kent became the focus of the nation's attention as, between 26 May and 3 June, more than 330,000 troops were rescued from the beaches in one of the most astonishing operations of the war.
Vice-Admiral Bertram Ramsay masterminded Operation Dynamo from a bunker deep within the Dover cliffs.