After serving as governor of Plymouth, Knollys was sent in 1566 to Ireland, his mission being to obtain for the queen confidential reports about the conduct of the lord-deputy Sir Henry Sidney.
He discussed religious questions with his prisoner, although the extreme Protestant views which he put before her did not meet with Elizabeth's approval, and he gave up the position of guardian just after his wife's death in January 1569.
In 1584 he introduced into the House of Commons, where since 1572 he had represented Oxfordshire, the bill legalising the national association for Elizabeth's defence, and he was treasurer of the royal household from 1572 until his death on 19 July 1596.
William inherited his father's estates in Oxfordshire (his eldest brother Henry having died without sons in 1583) and became in 1596 a privy councillor and comptroller, and subsequently treasurer, of the royal household.
[1] Some of Sir Francis Knollys's letters are in T. Wright's Queen Elizabeth and Her Times (1838) and the Burghley Papers, edited by S. Haynes (1740); and a few of his manuscripts are still in existence.
A speech which Knollys delivered in parliament against some claims made by the bishops was printed in 1608 and again in W. Stoughton's Assertion for True and Christian Church Policie (London, 1642).
[1] The Earl of Banbury's wife, Elizabeth Howard, who was nearly forty years her husband's junior, was the mother of two sons, Edward (1627–1645) and Nicholas (1631–1674), whose paternity has given rise to much dispute.
The House of Lords declared that he was not a peer and therefore not so entitled, but the Court of King's Bench released him from his imprisonment on the ground that he was the Earl of Banbury and not Charles Knowles, a commoner.
He dissipated an estate of £20,000 a year and appears to have had so loose a grasp of the concept of marriage that the word bigamous did not even begin to describe his conjugal exploits.
The Naval Chronicle of 1799 stated that "…he was the natural son of an earl of Bambury….and a French gentlewoman of rank and uncommon beauty, whom he seduced: circumstances made her case to be pitied and she was much noted by Lord and Lady Wallingford."
Several peers, including the great Lord Erskine, protested against this decision, but General Knollys himself accepted it and ceased to call himself Earl of Banbury.