Roundheads were the supporters of the Parliament of England during the English Civil War (1642–1651). Also known as Parliamentarians, they fought against King Charles I of England and his supporters, known as the Cavaliers or Royalists, who claimed rule by absolute monarchy and the principle of the divine right of kings. The goal of the Roundheads was to give to Parliament the supreme control over executive administration of the country/kingdom.
A Roundhead as portrayed by John Pettie (1839–1893)
A Roundhead inquisitor asks a son of a Cavalier, "And when did you last see your father?"—William Frederick Yeames (1878).
The Parliament of England was the legislature of the Kingdom of England from the 13th century until 1707 when it was replaced by the Parliament of Great Britain. Parliament evolved from the great council of bishops and peers that advised the English monarch. Great councils were first called Parliaments during the reign of Henry III. By this time, the king required Parliament's consent to levy taxation.
Parliament of England
A 16th-century depiction of the Parliament of King Edward I.The lords spiritual are seated to the king's right, the lords temporal to his left, and in the centre sit the justices and law officers.
Between 1352 and 1396, the House of Commons met in the chapter house of Westminster Abbey.
Queen Elizabeth I presiding over Parliament, c. 1580 – c. 1600