Sir Thomas Smith, who was Secretary of State to King Edward VI., and afterwards to Queen Elizabeth, was born at Saffron Walden, Essex, on the 23rd of December 1513. He was the son of John Smith of Saffron Walden and Agnes Charnock, a member of an old Lancashire family. When eleven years old he was sent to Queens' College, Cambridge, as he himself informs us in his Autobiographical Notes, now preserved in the British Museum,[14] which he wrote for the purpose of having his nativity cast: '1525. Sub fine II ani circa festu Michis Cantabrigiam su missus ad bonas I[=r]as.' Here he so greatly distinguished himself that King Henry VIII. chose him and John Cheke, afterwards tutor to Prince Edward, to be his scholars, and allotted them salaries for the encouragement of their studies. Cheke makes mention of this honour in an epistle to the King prefixed to his edition of Two Homilies of St. John Chrysostom, published at London in 1543: 'Cooptasti me et Thomam Smithum socium atque Æqualem meum, in scholasticos tuos.' Smith specially applied himself to the study of the Greek classics, and also to the reformation of the faulty pronunciation of the Greek language which then prevailed; and in a short time, so Strype, in his Life of Sir T. Smith, tells us, his more correct way 'prevailed all the University over.' He also endeavoured to introduce a new English alphabet of twenty-nine letters, and to amend the spelling of the time, 'some of the syllables,' he considered, 'being stuffed with needless letters.' As early as 1531 he had become a Fellow of his college, and in 1534 he was chosen University Orator. In 1540 Smith paid a visit to the Continent, and proceeded to Padua, where he took the degree of D.C.L. On his return to England in 1542 he was made LL.D. at Cambridge, and at the beginning of 1544 was appointed Regius Professor of Civil Law at the University. In the succeeding year he served as Vice-Chancellor, and also became Chancellor to Goodrich, Bishop of Ely, by whom in 1546 he was collated to the rectory of Leverington, Cambridgeshire, and also ordained priest, a fact unknown to Strype. About the same time he received a prebend from the Dean of Lincoln, and soon after he became Provost of Eton and Dean of Carlisle. Towards the end of February 1547, Smith was summoned to court, and 'mutata clericali veste, modoque, ac vivendi forma,'[15] he was made Clerk of the Privy Council, and Master of the Court of Requests of the Duke of Somerset, then Lord Protector. On the 14th of April 1548 he was sworn one of the King's Secretaries, and knighted in the beginning of the following year. Shortly after his appointment Smith was sent as ambassador to the Emperor Charles V., and in 1551 he took part in the embassy to France to arrange a match for the King with the French sovereign's eldest daughter. On the accession of Mary he lost all his offices and preferments, but he managed to pass through this dangerous reign in safety; and Strype says of him, 'that when many were most cruelly burnt for the profession of the religion which he held, he escaped, and was saved even in the midst of the fire, which he probably might have an eye to in changing the crest of his coat-of-arms, which now was a salamander living in the midst of a flame; whereas before it was an eagle holding a writing-pen flaming in his dexter claw.' When Elizabeth came to the throne, Smith returned to court, and was engaged in several embassies to France. In 1572 the Queen conferred on him the Chancellorship of the Order of the Garter; and shortly afterwards, on Lord Burghley's preferment to the office of Lord Treasurer, vacant by the death of the Marquis of Winchester, made him Secretary of State, a post which, four-and-twenty years before, he held under Edward VI. Smith died at his residence called Mounthaut, or Hill-hall, in Essex on the 12th of August 1577, and was buried in the parish church of Theydon Mount, where a monument was erected to his memory. He was twice married, but had no children by either of his wives.

Sir Thomas Smith possessed a fine library of about a thousand volumes. He bequeathed all his Latin and Greek books, as well as his great globe, of his own making, to Queens' College, Cambridge, or, if that college did not care to have them, to Peterhouse. Some of his Italian and French books he gave to the Queen's Library, and many volumes were also left to friends. Strype gives a list of the contents of the library at Hill-hall in 1566.

Smith was the author of several works, the principal one being De Republica Anglorum; the Maner of Gouvernement or Policie of the Realm of England, London, 1583, 4to. Between 1583 and 1640 this work passed through ten editions, and several Latin and other translations of it have been published.

A portrait of him by Holbein is at Theydon Mount, and another is preserved at Queens' College, Cambridge.