The Blue Ensign is a flag, one of several British ensigns, used by certain organisations or territories associated or formerly associated with the United Kingdom. It is used either plain or defaced with a badge or other emblem. The evolution of the Blue Ensign followed that of the Union Jack. The ensign originated in the 17th century with the St George's Cross (the Flag of England) in the canton, and with a blue field. The Acts of Union 1707 united England and Wales with Scotland in the Kingdom of Great Britain, thus producing a new Blue Ensign with the new Union Flag, containing a saltire, in the canton. With the Act of Union 1800, Ireland became a part of the new United Kingdom of Great Britain and Ireland, and St Patrick's Cross was incorporated into the Union Flag and, accordingly, into the cantons of all British ensigns from 1 January 1801. File:Government Ensign of the United Kingdom.svg|{{FIAV|000010}} The modern Blue Ensign of the United Kingdom File:British-Blue-Ensign-1707.svg|{{FIAV|historical}} The British Blue Ensign (1707–1801) File:English Blue Ensign 1620.svg|{{FIAV|historical}} English Blue Ensign as it appeared in the seventeenth century Prior to the reorganisation of the Royal Navy in 1864, the plain blue ensign had been the ensign of one of three squadrons of the Royal Navy, the Blue Squadron. This changed in 1864, when an order in council provided that the Red Ensign was allocated to merchantmen, the Blue Ensign was to be the flag of ships in public service or commanded by an officer in the Royal Naval Reserve, and the White Ensign was allocated to the Navy. Thus, since 1864, the plain blue ensign (without any defacement or modification) is permitted to be worn, instead of the Red Ensign, by three categories of civilian vessel: British merchant vessels whose officers and crew include a certain number of retired Royal Navy personnel or Royal Naval Reservists, or are commanded by an officer of the Royal Naval Reserve in possession of a Government warrant.