Received this PHQ card addressed to me with the same stamp fixed on other side, from Ms. Eileen, UK through postcrossing.com.
Royal Mail brought a special issue of 8 stamps and a miniature sheet with 4 stamps on "Britain Alone". It is Royal Mail’s tribute, 70 years on, to those who stood proud and defiant against the Axis powers in the dark days of 1940.
The Battle of Dunkirk was a battle in the Second World War between the Allies and Germany. A part of the Battle of France on the Western Front, the Battle of Dunkirk was the defence and evacuation of British and allied forces in Europe from 24 May-4 June 1940.
The above stamp shows two boats packed with evacuees from Dunkirk, France heading back to UK.
British propaganda later exploited the successful evacuation of Dunkirk in 1940, and particularly the role of the "Dunkirk little ships", very effectively. Many of the "little ships" were private vessels such as fishing boats and pleasure cruisers, but commercial vessels such as ferries also contributed to the force, including a number from as far away as the Isle of Man and Glasgow. These smaller vessels, guided by naval craft across the Channel from the Thames Estuary and from Dover, assisted in the official evacuation. Being able to reach much closer in the beachfront shallows than larger craft, the "little ships" acted as shuttles to and from the larger craft, lifting troops who were queuing in the water, many waiting shoulder-deep in water for hours. The term "Dunkirk Spirit" still refers to a popular belief in the solidarity of the British people in times of adversity.
Source: Wikipedia, Royalmail.com