England was a monarchy for the entirety of its political existence since its creation about 927 up to the 1707 Act of Union, except for the eleven years of English Interregnum (1649 to 1660) that followed the English Civil War.
The rule of executed King Charles I of England was replaced by that of a republic known as Commonwealth of England (1649–1653). The most prominent general of the republic, Oliver Cromwell, managed to extend its rule to Ireland and Scotland.
The victorious general eventually turned against the republic, and established a new form of government known as The Protectorate, with himself as Lord Protector until his death on September 3, 1658. He was succeeded by his son Richard Cromwell. However, anarchy eventually developed, as Richard proved unable to maintain his rule. He resigned his title and retired into obscurity. The Commonwealth was re-established but proved unstable. The exiled claimant Charles II of England was recalled to the throne in 1660 in the English Restoration.
https://en.wikipedia.org/wiki/Kingdom_of_England
Prior to 1926, the British Empire was structured such that the British Crown reigned over the empire collectively, each of its Dominions and Crown colonies being subordinate to the United Kingdom. The Balfour Declaration of 1926 provided the Dominions the right to be considered equal to Britain; this effectively created a system whereby a single monarch operated independently in each Commonwealth realm rather than as part of a unitary British Crown reigning over the United Kingdom and all the Dominions as one body. The monarchy thus ceased to be an exclusively British institution, although it is often still referred to as "British" for legal and historical reasons, as well as for convenience.
The first indication of this shift in constitutional law was the Royal and Parliamentary Titles Act, 1927, and the concept was further solidif
