The Blue Ensign is a distinctive flag, originally flown by British naval vessels, and later by ships run by government and certain public bodies. The design features a blue field with the Union Jack in the top left corner, known as the 'canton', and a badge, signifying rank or nationality, on the right-hand side or 'fly'. It acts not only as a symbol of nationality, but also serves as an identification of the specific organization or governmental body associated with the ship. The use of the Blue Ensign is governed by a comprehensive set of regulations set forth by the British government.

1. The British Antarctic Territory still uses the Blue Ensign flag; it's a vivid blue with a Union Jack in the upper left corner and the territory's coat of arms on the right. 2. The Royal Fleet Auxiliary, a civilian-manned fleet owned by the UK's Ministry of Defence, flies a Blue Ensign adorned with a gold anchor to denote its connection with the Royal Navy. 3. British government vessels that are not commissioned warships, such as certain boats of the Border Force, research ships of Natural Environment Research Council, and vessels of the Royal Voluntary Service, also use a Blue Ensign. 4. Civilian ships rented for government service in the UK are authorized to fly a blue ensign. This flag has the Union Jack in the canton, with the seal or shield of the department in the fly. 5. The Blue Ensign flown on Royal Yacht Club boats is adorned with a St. George’s Cross and a crown in the middle to mark the royal charter. This version of the Blue Ensign is used by certain yacht clubs to indicate that they have received a royal charter from the British monarchy.

The Blue Ensign is a distinctive British flag, consisting of a dark blue field with the Union Jack in the canton (upper left corner). However, not just any British ship can fly this flag! In order to fly the Blue Ensign, a British ship must either be operating on government service or have earned a special warrant issued by the Central Chancery of the Orders of Knighthood. This warrant may be granted to civilian ships that have officers and crew members who are serving or retired members of the Royal Naval Reserve. So while the Blue Ensign might not be the most common flag you see on the high seas, if you do spot one, you'll know that ship has a special connection to the British government or royal navy! Striking and unique, this flag has a rich history of use and continues to be a distinctive emblem of certain British ships today.