[1] Clarke was made clerk extraordinary of the Privy Council in 1620, successor to William Beecher, and was introduced at court by Buckingham.
[1] In September 1623 he was entrusted by Charles with secret orders to Lord Bristol, then British ambassador at Madrid, for the postponement of the Spanish Match.
For an attempted defence of Buckingham he was on 6 August 1625 imprisoned by the House of Commons at Oxford.
[2] The next year Buckingham tried to persuade the small electorate of Bridport, Dorset to return Clarke to Parliament, as they had already done for Sir Richard Strode, another of Buckingham's nominees, but they refused on the grounds that they had promised the second seat for the constituency to Sir Lewis Dyve.
In 1627 he was sent on a mission to Christian IV of Denmark, then beset in the Thirty Years' War by Imperial forces.