England and Wales
Lieutenants were first appointed to a number of English counties by King Henry VIII in the 1540s, when the military functions of the sheriff were handed over to him. He raised and was responsible for the efficiency of the local militia units of the county, and afterwards of the yeomanry, and volunteers. He was commander of these forces, whose officers he appointed. These commissions were originally of temporary duration, and only when the situation required the local militia to be specially supervised and well prepared; often where invasion by Scotland or France might be expected.
Lieutenancies soon became more organised, probably in the reign of his successor King Edward VI, their establishment being approved by the English parliament in 1550. However, it was not until the threat of invasion by the forces of Spain in 1585 that lieutenants were appointed to all counties and counties corporate and became in effect permanent. Although some counties were left without lieutenants during the 1590s, following the defeat of the Spanish Armada, the office continued to exist, and was retained by King James I even after the end of the Anglo-Spanish War.
The office was abolished under the Commonwealth, but was re-established following the Restoration under the City of London Militia Act 1662, which declared that:
[T]he King's most Excellent Majesty, his Heirs and Successors, shall and may from Time to Time, as Occasion shall require, issue forth several Commissions of Lieutenancy to such Persons as his Majesty, his Heirs and Successors, shall think fit to be his Majesty's Lieutenants for the several and respective Counties, Cities and Places of England and Dominion of Wales, and Town of Berwick upon Tweed.
Although not explicitly stated, from that date lieutenants were appointed to "counties at large", with their jurisdiction including the counties corporate within the parent county. For example, lieutenants of Devon in the seventeenth and eighteenth centuries appointed deputy lieutenants to the City of Exeter, and were sometimes described as the "Lieutenant of Devon and Exeter" The one exception was Haverfordwest, to which a lieutenant continued to be appointed until 1974. The origin of this anomaly may have lain in the former palatine status of Pembrokeshire.
The City of London was uniquely given a commission of lieutenancy, and was exempt from the authority of the lieutenant of Middlesex. The Constable of the Tower of London and the Warden of the Cinque Ports were ex-officio lieutenants for the Tower Hamlets and Cinque Ports respectively, which were treated as counties in legislation regarding lieutenancy and militia affairs.
The official title of the office at this time was His or Her Majesty's "Lieutenant for the county of x", but as almost all office-holders were peers of the realm, they were referred to as "Lord-Lieutenant".
An Act to make the Militia of this Kingdom more useful (Geo 2, c.9) was passed by the Parliament of Ireland in 1715. This provided for the issuing of commissions to appoint persons as "his Majesty's lieutenant or lieutenants, governor or governors, and commissioners of array for the several and respective counties, cities, and places of Ireland". The lieutenants were empowered to embody militia regiments. When the Irish Free State became independent of the UK in 1922, British rule ceased to exist.
In 1921, with the establishment of Northern Ireland, lord lieutenants continued to be appointed through the Governor of Northern Ireland to the six counties and two county boroughs. In 1973 the counties and county boroughs were abolished as local government units in Northern Ireland, and lord-lieutenants are now appointed directly by the Queen to "counties and county boroughs... as defined for local government purposes immediately before 1 October 1973".
Although Colin, Earl of Balcarres was appointed Lord Lieutenant of Fife in 1688, and lieutenants were appointed to a few counties from about 1715, it was not until 1794 that permanent lieutenancies were established by Royal Warrant. By the Militia Act 1797, the lieutenants appointed "for the Counties, Stewartries, Cities, and Places" were given powers to raise and command county militia units.
The Lord Provosts of Edinburgh, Glasgow, Aberdeen, and Dundee are, by virtue of office, also the lord-lieutenant of their respective city.
While in their lieutenancies, lord-lieutenants are among the few individuals in Scotland officially permitted to fly the banner of the Royal Arms of Scotland, or "The Lion Rampant" as it is more commonly known.