The Royal Navy used the White Ensign in conjunction with the Red and Blue, due to the rank structure employed at the time. Each grade of admiral (rear-, vice- and full) was sub-divided into levels of seniority: red, white, and blue. Ships attached to an admiral's squadron would then fly the ensign appropriate to that particular admiral.
In 1864 the Admiralty decided to end the ambiguity caused by the Red Ensign being both a civil ensign and a naval ensign, and the White Ensign was reserved to the Royal Navy; the relevant Order in Council retained the option to use Red or Blue Ensigns in HM Ships if desired.
