English Civil War

English Civil War (1642–1651) waged between Parliamentarians (“Roundheads”) and Royalists (“Cavaliers”) primarily over the manner of England’s governance and issues of religious freedom.
Royalists supported King Charles I and his absolute authority, while the Parliamentarians sought to curb the King’s powers and championed constitutional monarchy.
The war resulted in the temporary overthrow of the monarchy, putting Oliver Cromwell in power and leading to a de facto republic, known as the Commonwealth of England.
This period saw the rise of the New Model Army, a military unit established by the Parliamentarians, which was distinct due to its full-time, professional soldiers and meritocratic officer appointment.
The Civil War resolved, for a time, the King-in-Parliament question, a central issue in British constitutional history. The victory of Parliamentarians reinforced the notion that a monarch could not govern without Parliament’s consent.

Interregnum and Commonwealth

The Interregnum (1649-1660) refers to the period between the execution of Charles I and the restoration of Charles II when England and Wales, later along with Scotland and Ireland, were ruled as a republic.
During this time, parliamentary supremacy was reinforced under military dictator Oliver Cromwell who ruled as Lord Protector.
England’s brief period as a republic, referred to as The Protectorate, saw further religious freedom and tolerance.

Restoration

The monarchy was restored in 1660, in an event known as the Restoration. Charles II, son of the executed Charles I, returned to reign over England.
The government form devised during this time, known as the Clarendon Code, saw a tilt back towards monarchal power, but with significant concessions made to uphold parliamentary positions.

Remember: The English Civil War, and the subsequent Interregnum were crucial periods in shifting the balance of power from the monarchy to parliament, forming the foundations of the parliamentary democracy we see in the UK today.