Lord Protector

Lord Protector is a title that has been used in British constitutional law for the head of state. It was also a particular title for the British heads of state in respect to the established church. It was sometimes used to refer to holders of other temporary posts; for example, a regent acting for the absent monarch.

Feudal royal regent

The title Lord Protector was originally used by royal princes or other nobles exercising a role as protector and defender of the realm, while also sitting on a regency council, governing for a monarch who was unable to do so.
Notable cases in England:

John of Lancaster, Duke of Bedford, and Humphrey, Duke of Gloucester, were jointly Lords Protector for Henry VI ;
Richard Plantagenet, Duke of York, was three times Lord Protector for Henry VI;
Richard, Duke of Gloucester, was "Lord Protector of the Realm" during the nominal reign of Edward V before being offered the throne as Richard III;
Edward Seymour, Duke of Somerset, was Lord Protector during the early years of the reign of the young Edward VI;

and in Scotland:

John Stewart, Duke of Albany, was "Governor and Protector of the Realm" for James V of Scotland ;
James Hamilton, Duke of Châtellerault, was "Governor and Protector of the Kingdom" for Mary, Queen of Scots.
Cromwellian Commonwealth

The Lord Protector of the Commonwealth of England, Scotland and Ireland was the title of the head of state and head of government during the Commonwealth, following the first period when a Council of State held executive power. The title was held by Oliver Cromwell and subsequently his son and designated successor Richard Cromwell during what is now known as The Protectorate.
The 1653 Instrument of Government stated:
The replacement constitution of 1657, the Humble Petition and Advice, gave "His Highness the Lord Protector" the power to nominate his successor. Cromwell chose his eldest surviving son, the politically inexperienced Richard. That was a non-representative and de facto dynastic mode of succession, with royal connotations in both styles awarded and many other monarchic prerogatives, such as that of awarding knighthoods.
Richard Cromwell, who succeeded after his father's death in September 1658, held the position for only eight months before he resigned in May 1659. He was followed by the second period of Commonwealth rule until the Restoration of the exiled heir to the Stuart throne, Charles II, in May 1660.

Lords Protector (1653–1659)

Post-Cromwell

Since the Restoration the title has not been used in either of the above manners. George, Prince of Wales, appointed to the regency in 1811, was referred to as "His Royal Highness the Prince Regent". George exercised the powers of the monarchy, just as Lords Protector had, but the title's republican associations had rendered it distasteful.

Protector of the church

'Lord Protector' has also been used as a rendering of Latin Advocatus in the sense of a temporal Lord who acted as the protector of the mainly secular interests of a part of the church; compare the French title of vidame.

In fiction

In the novel The Last Man by Mary Shelley, Britain becomes a republic with its elected head of state styled as Lord Protector. The title is held by Lord Raymond, and Ryland. In the 1987 television series The New Statesman's finale episode, "The Irresistible Rise of Alan B'Stard", after B'Stard's New Patriotic Party wins a landslide majority in a special general election called over British membership of the European Economic Community but with himself not having contested a seat, he briefly considered adopting the title of Lord Protector before being permitted to serve as an extra-parliamentary prime minister. In the 2008 film adaptation of C. S. Lewis' children's novel Prince Caspian, the antagonist Miraz begins as Lord Protector of Narnia before being proclaimed King. In the 2020 film Wolfwalkers the Lord Protector serves as its primary antagonist.