The Dunkirk Jack
The St George’s Cross defaced with the arms of Dunkirk flown from the jack staff is known as the Dunkirk jack and is only flown by civilian ships and boats of all sizes that took part in the Dunkirk rescue operation in 1940. The only other ships permitted to fly the George’s Cross flag at the bow are those with a Royal Navy Admiral on board.
“Permission was given by the Admiralty, the College of Heralds and the City of Dunkirk for the Cross of St. George (the flag of Admiralty) to be defaced with the Arms of Dunkirk for use as the Association’s House Flag. This can be worn by Member Ships at any time when the owner is aboard. In addition, when in company, we fly the undefaced Cross of St. George at the bow.
“To avoid any possible confusion with barges wearing an Admiral’s flag, the Dunkirk Little Ships must wear the Red Ensign when flying the undefaced Flag of St. George at the bows…”
–source: Jacks of the UK
above right: St George’s Cross
below right: Blason ville fr Dunkerque:
“A lion sable passant armed and langued gules, argent a dolphin azure naiant embowed finned and langued gules. In other words, picturing a (former) Flemish city and harbour.”
The Flag of England is the St George’s Cross. The red cross appeared as an emblem of England in the Middle Ages, specifically during the Crusades (although the original symbol used to represent English crusaders was a white cross on a red background) and is one of the earliest known emblems representing England. It also represents the official arms of the Most Noble Order of the Garter, and it achieved status as the national flag of England during the sixteenth century.
The flag used by the British Royal Navy (the White Ensign) is also based on the flag of England, consisting of the St George’s Cross and a Union Flag in the canton. In addition to the UK, several countries in the Commonwealth of Nations also have variants of the White Ensign with their own national flags in the canton, with the St George’s Cross sometimes being replaced by a naval badge.
more: History of the Union Jack on wikipedia