The documents of the years 1642-60, though relatively few, are entitled to occupy a section by themselves because they represent a period unique in English history. Civil conflict and revolutionary government mark off the Interregnum as a gap in an otherwise unbroken story of constitutional growth, and impart to the pertinent documents a novelty that will be obvious even to the beginning student.

The war not only compelled the adoption of such practical measures as those placed under nos. 100 and 101, but also inspired the condemnation of the king and the abolition of the monarchical system (nos. 104, 106, 107). At the same time these revolutionary enactments called forth arguments for their justification and induced the parliamentary leaders to make noteworthy experiments in constructive reform. For the first and only time in English history, the state was given a written constitution — the Instrument of Government, led up to by a number of suggestions (among them nos. 102, 103, 105) and eventually amended by the Humble Petition and Advice in 1657. Short-lived as it was, this work of political innovation deserves careful study — if for no other reason, because it somewhat anticipated such measures as the great Reform Act of 1832. To the Commonwealth and Protectorate were also due the first governmental union of England, Wales, Scotland, and Ireland; the first establishment within them of even partial religious toleration; and the first practical recognition of economic solidarity between the mother country and the colonies — by the Navigation Act of 1651. Therefore, when viewed in perspective from the present day, the acts of the Interregnum have their place in the institutional development of England.

By the year 1642 it was already an established tradition for Englishmen to be interested in all phases of government. The Interregnum, being an age of violent partisanship and of revolutionary change, naturally roused that interest to a new height. The result was a profusion of memoirs, diaries, books, and pamphlets of all sorts. Among them are many works — especially those of John Milton, James Harrington, and Thomas Hobbes — that occupy commanding places in the history of political thought.

Much of this literature, as well as the contemporary activity in practical government and administration, is treated in the following monographs: E. Jenks, The Constitutional Experiments of the Commonwealth; T. C. Pease, The Leveller Movement; G. P. Gooch, English Democratic Ideas in the Seventeenth Century; and C. H. Firth, The House of Lords during the Civil War. The constitutional history of the Interregnum also falls within the scope of more general books, such as Gardiner's History of the Great Civil War and History of the Commonwealth and Protectorate; Firth's Last Years of the Protectorate; and the numerous biographies of Oliver Cromwell. The two standard collections of pertinent sources are Gardiner, Constitutional Documents of the Puritan Revolution, and Firth and Rait, Acts and Ordinances of the Interregnum.