British ensigns

In British maritime law and custom, an ensign is the identifying flag flown to designate a British ship, either military or civilian. Such flags display the United Kingdom Union Flag in the canton (the upper corner next the staff), with either a red, white or blue field, dependent on whether the vessel is civilian, naval, or in a special category. These are known as the red, white, and blue ensigns respectively.

Outside the nautical sphere, ensigns are used to designate many other military units, government departments and administrative divisions. These flags are modelled on the red, white, and blue naval ensigns, but may use different colours for the field, and be "defaced" by the addition of a badge or symbol, for example the sky blue with concentric red, white and blue circles of the Royal Air Force ensign.

The Union Flag (also known as the Union Jack) should be flown as a jack by Royal Navy ships only when moored, at anchor, while underway and dressed with masthead ensigns, or if the Monarch or an Admiral of the Fleet is on board. The Union Flag may also signal that a court martial is in progress.

The use of the Union Flag as an ensign on a civilian craft is still illegal, ever since Charles I ordered it be restricted to His Majesty's ships "upon pain of Our high displeasure" in the 17th century, mainly due to its unauthorised use by merchant mariners to avoid paying harbour duties by passing themselves off as Royal vessels.

British ensigns currently in use can be classified into five categories, in descending order of exclusivity:

The traditional order of seniority was red, white and blue, with the red as the senior ensign.

Today's white ensign, as used by Royal Navy ships, incorporates the St George's Cross (St George's Ensign). British yachts owned by members of the Royal Yacht Squadron are authorised to apply for a permit to wear this ensign. Defaced white ensigns include that of the British Antarctic Territory.

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