quality:correction
English civil war era

On 4 January 1649, the Rump Parliament declared "that the people are, under God, the original of all just power; that the Commons of England, being chosen by and representing the people, have the supreme power in this nation".

The English Protectorate set up by Oliver Cromwell after the English Civil War promulgated the first detailed written constitution adopted by a modern state; it was called the Instrument of Government. This formed the basis of government for the short-lived republic from 1653 to 1657 by providing a legal rationale for the increasing power of Cromwell after Parliament consistently failed to govern effectively. Most of the concepts and ideas embedded into modern constitutional theory, especially bicameralism, separation of powers, the written constitution, and judicial review, can be traced back to the experiments of that period. Drafted by Major-General John Lambert in 1653, the Instrument of Government included elements incorporated from an earlier document " Heads of Proposals ", which had been agreed to by the Army Council in 1647, as a set of propositions intended to be a basis for a constitutional settlement after King Charles I was defeated in the First English Civil War. Charles had rejected the propositions, but before the start of the Second Civil War, the Grandees of the New Model Army had presented the Heads of Proposals as their alternative to the more radical Agreement of the People presented by the Agitators and their civilian supporters at the Putney Debates. The Instrument of Government was adopted by Parliament on 15 December 1653, and Oliver Cromwell was installed as Lord Protector on the following day. The constitution set up a state council consisting of 21 members while executive authority was vested in the office of " Lord Protector of the Commonwealth." This position was designated as a non-hereditary life appointment. The Instrument also required the calling of triennial Parliaments, with each sitting for at least five months.

The Instrument of Government was replaced in May 1657 by England's second, and last, codified constitution, the Humble Petition and Advice, proposed by Sir Christopher Packe. The Petition offered hereditary monarchy to Oliver Cromwell, asserted Parliament 's control over issuing new taxation, provided an independent council to advise the king and safeguarded "Triennial" meetings of Parliament. A modified version of the Humble Petition with the clause on kingship removed was ratified on 25 May. This finally met its demise in conjunction with the death of Cromwell and the Restoration of the monarchy.