The definition of which bodies should be classified as parliaments becomes increasingly problematic before the accession of the Tudor monarchs, starting with Henry VII of England.
columns in the tables below contain the number counting forward from the accession of particular monarchs of England before 1660 (or the Commonwealth and Protectorate regimes of the 1650s).
It replaced the earlier Anglo-Saxon institution of the Witenagemot, which had a similar mix of important clerical and lay members, but different powers.
The Curia Regis (known in English as the council or court) was composed of prominent church leaders (archbishops, bishops and some abbots) and the king's feudal tenants-in-chief (in effect the landowning aristocracy, the earls and barons).
The earliest known official use was by the Court of King's Bench which in November 1236 adjourned a case to be heard at a parliamentum at Westminster due on the following 13 January.
It passed certain legislation, which constitutes the first entry in the official collection of the statutes of England, published in the nineteenth century.
It may be that the meeting at Merton involved no innovation, but owes its prominence to the chance survival of some records which were copied into a collection of statutes from the second half of the fourteenth century.
Powell and Wallis confirm that a copy of the writ of summons has survived, possibly the earliest still in existence.
Dramatic political events at the meeting were recorded by the chronicler Matthew Paris, so it is known that the king asked for a tax, which the council (retrospectively dubbed a parliament) refused to grant.
They were composed of important church officials and landowners, whom the king summoned individually to advise him, similar to the group of men which eventually became known as the House of Lords.
The sheriffs of the English counties were ordered to send knights of the shire to attend a number of parliaments before 1265, but they were not required to have them chosen by election.