Sir William Trumbull, the Secretary of State, was son and heir of William Trumbull (1594-1668). The latter was the son of William Trumbull Senior (d.1635), the English Ambassador to the Netherlands. He had graduated as a BA from Magdalen College, Oxford on 19th February 1625, became a student of the Middle Temple in 1626 and then clerk to the signet, as well as Justice of the Peace for the county of Berkshire. Sir William’s mother was Elizabeth, only daughter of George Rudolph Weckerlin, Latin Secretary to King Charles I. She died on 11th July 1652 in her thirty-third year, when he was only thirteen.

Trumbull was born at Easthampstead Park in Berkshire and baptised on 11th September 1639. He received his early instruction in Latin and French from his Grandfather Weckerlin and was sent, in 1649, to Wokingham School. On 6th April 1666, he matriculated at St. John's College, Oxford, being entered as a gentleman-commoner under the Rev. Thomas Wyatt and, in 1667, was elected to a fellowship at All Souls' College, which he probably retained until his marriage in 1670. He graduated BOL on 12th October 1659, DCL 6th July 1667, and he was entered at the Middle Temple as a student in 1667. After taking his degree, he visited France and Italy, where he made the acquaintance of several distinguished persons, such as Lords Sunderland and Godolphin, Algernon Sidney and Compton (afterwards Bishop of London). In 1664 and 1666, he travelled in company with Sir Christopher Wren and Edward Browne, eldest son of Sir Thomas Browne.

In 1666 Trumbull returned to college and entered upon active life in the profession of the law. During 1667, practising "as a civilian in the vice-chancellor's court at Oxford, he appealed to the chancellor, Clarendon, and carried a point respecting the non-payment of fees for his doctor's degree, gained great credit by it and all the business of the court". He was admitted an advocate in the college of Doctors' Commons on 28th April 1668 and began practising in the ecclesiastical and admiralty courts. Several opportune changes among the advocates practising in his courts during 1672 brought him much business with an income of £500 per annum. He was appointed to the chancellorship of the diocese of Rochester and obtained the reversion, after the death of Sir Philip Warwick in 1682, of the post of clerk of the signet.

Trumbull went to Tangier, under Lord Dartmouth, and, in the company of Pepys and others, in August 1683, with a promise that he should be at home again in six weeks. His appointment was as judge-advocate of the fleet and commissioner for settling the leases of the houses between the King and the inhabitants. Pepys at once makes a note, "Strange to see how surprised and troubled Dr. Trumbull shows himself at this new work put on him of a judge-advocate; how he cons over the law-martial and what weak questions he asks me about it". The expedition set sail from St. Helen's on 19th August 1683 and arrived in Tangier Bay on 14th September. Trumbull grumbled much over the business and complained that "he should have gotten ten guineas the first day of term." Pepys calls him "a man of the meanest mind as to courage that ever was born" and, on 20th October, adds, with perhaps an excess of disdain, "So the fool went away, every creature of the house laughing at him". On 10th November 1683, Trumbull returned to Whitehall. The journal of the commissioners and their report on the valuation of the properties are among Lord Dartmouth's manuscripts.

On the promotion of Godolphin in August 1684, the King thought, for a time, of Trumbull as his successor in the post of Secretary of State. Shortly afterwards, he refused the office of Secretary of War in Ireland and, in the following November, he was presented, by Lord Rochester, to the King and knighted on 21st November 1684. On 1st February 1685, he was made clerk of deliveries of ordnance stores. By the King's command, and much against his own inclination, he was despatched, in November 1685, as envoy extraordinary to France and, as he could not retain his post of clerk of deliveries, he accepted, in lieu of it, a pension of £200 per annum, "the only pension he ever had."

Sir William was a zealous opponent of Roman Catholicism and did much to benefit the condition of the English Protestants in France after the revocation of the edict of Nantes. This did not commend him either to the French or English court and, in August 1686, he received letters of recall. His services to the Protestants were long held in remembrance. Bayle presented to him a copy of his dictionary and received, in return, a Latin letter styling the work 'bibliothecam potius quam librum.' Several of Bayle's friends wished him to dedicate the work to Trumbull, and Pierre Sylvestre wrote that it was rare indeed to find such a Maecenas. Motteux dedicated to him his translation of St. Olon's 'Present State of Morocco' (1695), acknowledging his charity to many of the French refugees and his bounty to himself.

Through the favour of the Trelawny family, Trumbull sat from 1685 to 1687 for the Cornish borough of East Looe. In November 1686, he was made Ambassador to the Porte and embarked for Constantinople on 16th April 1687. An account of his receptions at Leghorn, Pisa and Florence is among the manuscripts of Mr. Cottrell Dormer. He was a Governor of the Hudson's Bay and the Turkey Companies and, just before his departure for the East, the latter body gave him "a dinner at the Ship at Greenwich and presented his lady with a gold cup". His mission at Constantinople, where he arrived on 17th August 1687, having previously visited Smyrna and settled certain matters there, was attended by success and, at the desire of the Turkey merchants, he was renominated in November 1689 and continued there until 31st July 1691. His narrative of events which occurred in Turkey to the close of April 1688 is contained in Addit. MS. 34799 (British Library), and much of its substance was used by Sir Paul Rycaut in his history of the Turks, in continuation of Knolles (1700).

Trumbull was made a Lord of the Treasury on 3rd May 1694. Exactly a year later, he was elevated to the position of Secretary of State, in succession to Sir John Trenchard, and made a privy councillor. A few days afterwards, he became secretary to the seven lords-justices of England in the King's absence. At the general election in 1695, he was returned for the Yorkshire borough of Hedon and for the University of Oxford, when he chose the latter constituency, and sat for it until the dissolution in 1698. Trumbull, a man "of moderate opinions and of temper cautious to timidity . . . hardly equal to the duties of his great place", after many attempts to withdraw, resigned the seals very suddenly on 1st December 1697, complaining that the lords justices had treated him "more like a footman than a secretary". Lord Aylesbury speaks of him as less than a friend, "nor was he to any but your obedient humble servant to all, like my Lord Plausible in the ‘Plain Dealer’". One piece of Trumbull's advice to King William III deserves to be recorded: "Do not send embassies to Italy, but a fleet into the Mediterranean."

Trumbull withdrew from active life in 1698. He was offered, in May 1702, but declined, to be one of the Lord High Admiral's Council and, at a later date, he excused himself "upon the score of age and infirmities" from again accepting the seals. Elm Grove, on the edge of Ealing Common, had formerly been his residence, but he now settled himself at Easthampstead.

Trumbull's name is associated with two great literary undertakings. Dryden records, in the postscript to his translation of Virgil, that "if the last Aeneid shine amongst its fellows, it is owing to the commands of Sir William Trumbull, who recommended it as his favourite to my care." Alexander Pope made Trumbull's acquaintance about 1705. They "used to take a ride out together three or four days a week and at last almost every day," and their talk was of the classics. Pope showed him his translation of the 'Epistle of Sarpedon from the 12th and 16th Books of the Iliads,' and Trumbull, in his admiration, urged the young poet to translate the whole of Homer's works. The advice at last bore fruit.

Pope read his pastorals to the old statesman and 'Spring' was dedicated to him. In the published work, Trumbull is characterised as "too wise for pride, too good for pow'r," and as carrying into retirement "all the World can boast". Trumbull had suggested 'Windsor Forest,' of which he was verderer, as a subject for Pope. He had given him several hints and made some little alterations; but the credit was given, by Pope, to Granville, Lord Lansdowne, and Trumbull complained of the "slippery trick." Lines 237 to 258, however, are in praise of the man who retired from court to glades like those of Windsor, the man "whom Nature charms, and whom the muse inspires," and it ends with "Thus Atticus, and Trumbull thus retired." Pope evidently had a sincere liking for the old man. In his private memorandum of departed relatives and friends occurs his name with the words "amicus meus humauissimus a juvenilibus annis".

Trumbull died on 14th December 1716 and, on 21st December, was buried in Easthampstead Church. A handsome monument was placed to his memory in the south transept. In 1670, he had married his first wife, Katherine, daughter of Sir Charles Cotterell, Master of the Ceremonies, "a very beautiful and accomplished woman," whereupon his father settled upon him an income of £350 a year. She died without issue on 8th July 1704. He married, in Scotland, in October 1706, as his second wife, Judith (1681-1724), second daughter of Henry Alexander, 4th Earl of Stirling, who lived in Binfield (Berkshire). They had two children, Judith (1707-1708) and William (1708-1760), from whose only daughter and heiress, the wife of Martyn, fourth son of the 1st Baron Sandys, are descended the present Marquis of Downshire and Lord Sandys. Elijah Fenton was the tutor of the young Trumbull, from early in 1724, and died at Easthampstead in 1730. 'Lines by Sir Henry Sheers,' written to Sir William Trumbull's three nieces, are in 'Poems on several Occasions' appended to 'Prior's Poems' (1742).

Trumbull's character of Archbishop Dolben is printed in the 'History of Rochester' (1817) and in the second edition of the 'Biographia Britannica.' Many letters by him are in print or in manuscript, especially in the Public Record Office, the British Museum and the Downshire Papers, once held at Easthampstead Park, but now divided between the British Library and the Berkshire Record Office.

Jervas was engaged to paint a family picture of the Trumbulls and it hung, for many years, at Easthampstead. Sir William's portrait was also painted by Kneller and his bust, by Henry Cheere, is, with those of many other distinguished fellows of the college, in the library of All Souls'.

The politician's younger brother, Dr. Charles Trumbull (1646-1724), graduated as a BA from Christ Church, Oxford, in 1667, and DCL from All Souls' in 1677. Two years later, he became Rector of Hadleigh in Suffolk and Rector of Stisted in Essex; was Chaplain to Sancroft and followed his example in resigning his benefices upon the Revolution. He died on 3rd January 1724 .