William was son of John Trumbull of Craven in Yorkshire and his wife, Elizabeth Brogden. He seems to have been introduced at Court by Sir Thomas Edmondes, whom he afterwards described as his “old master.” Early in King James I's reign, he was a court messenger and was probably attached to Edmondes' embassy to the Archduke Albert of Austria, Regent of the Netherlands. When Edmondes was recalled from Brussels in 1609, Trumbull was promoted to succeed him as resident at the Archduke's Court. He retained this difficult post for sixteen years and his correspondence is a valuable source for the diplomatic history of the period. His salary was twenty shillings a day. On 6th June 1611, Trumbull was instructed to demand the extradition of the rebel claimants to the throne, William Seymour and Arabella Stuart, should they land in the Archduke's dominions. On 17th February 1614, after re­peated solicitation, he was granted an ordinary clerkship to the privy council; but the office seems to have been a sinecure, for Trumbull remained at his post at Brussels. In 1620, he protested against the Spanish invasion of the Palatinate. In 1624, he requested the reversion “of one of the six clerks' places” for himself and a clerkship of the privy seal for his eldest son. He was recalled, in 1625, upon the open rupture with Spain and, on 16th February 1626, he was returned to Parliament for Downton in Wiltshire. He assumed active duties as clerk of the Privy Council, devoting himself especially to Naval matters. On 26 March 1628, he was granted Easthampstead Park in Berkshire, on condition of maintaining a deer-park for the King's recreation. Soon afterwards, he was appointed Muster Master General. He died in London in September 1635, being succeeded as Clerk to the Council by his godson, (Sir) Edward Nicholas, and was buried in Easthampstead Church. By his wife, Deborah the daughter of Walter Downes of Beltring in Kent, he left two sons and two daughters. The elder son, William (1594-1668), was father of Sir William Trumbull, the Secretary of State during King William III’s reign.