A British merchant ensign from the Q-ship 'Mavis'. It is made of hand and machine-sewn wool bunting with a linen hoist marked 'RED ENSIGN 4 BDS'and '7314'. The hoist is pierced with eyelets and marked with the maker's name.

Royal Naval flags were traditionally measured in breadths across the hoist. This unit which related to the width in which the fabric was woven changed from about 11 inches in the 17th century to its modern definition of 9 inches (23cm).

Q-ships were small merchant vessels fitted with concealed armaments. They were intended as decoy ships, being small enough to tempt a U-boat to attack them on the surface. The Q-ship would then drop the shutters concealing her guns and return fire, having first lowered her merchant ensign and hoisted the White Ensign. The Q-ships were ballasted with timber to keep them afloat should they be torpedoed. 'Mavis' also known as 'Nyroca' or Q.26 was hired from 31 January 1917 to 27 July 1918. Her most notable exploit was the rescue of three survivors from the torpedoed Greek S.S. N 'Hadziaka' on 2 June 1917. She herself was torpedoed the following day, but owing to her ballast of firewood she remained afloat to be towed into Plymouth Sound and beached in Cawsand Bay.