In 1629, at Archbishop Laud's request, he drew up the Caroline cycle to regulate the election of proctors from the various colleges. About the same date he also served on a committee established to revise the university statutes.England had been governed by King Charles I from around 1629 without parliament being called, but when he needed to raise money to fight the Scots after being defeated by them in 1639 he decided to summon Parliament in April 1640 . After a second defeat by the Scots in August 1640 he again summoned Parliament in November 1640. Tensions rapidly rose between the King and Parliament, and late in 1641 both sides began to enlist troops. Sir John Byron began to enlist troops to support the King and Turner, a staunch Royalist, was one of the first to join Sir John Byron. The King moved to Oxford, setting up his court in Christ Church, while London was controlled by Parliament. There were initial skirmishes but the Civil War began in earnest with the Battle of Edgehill near Warwick in November 1643. Turner had been taken prisoner by the Parliamentary forces in one of the skirmishes and taken to London where he was imprisoned in Southwark. However in 1643 there was an exchange of prisoners between Parliament's side and the King's side and Turner was allowed to return to join the King in Oxford.
The King largely had the best of the military exchanges in 1644 but the tide changed in 1645 when the King was defeated at the Battle of Naseby. The success of Cromwell for the Parliamentary side was a decisive factor and the King suffered further defeats during the rest of 1645. By the spring of 1646 Oxford was surrounded by Parliament's forces but the King escaped and joined the Scottish covenanters. They handed him over to Parliament in 1647 and by 1648 Parliament was totally in control of the country. On 9 November 1648 representatives of Parliament removed Turner from his fellowship at Merton and from the Savilian chair of Geometry. He had strongly supported the Royalist cause during the Civil War and served in a military capacity from 1641 so there was no way that Parliament was going to allow him to continue to hold these influential positions. With no means of financial support, Turner went to live with his sister in Southwark. She had married a brewer named Wats but her husband had died. He lived out his final years in total poverty.
Turner's quality as a mathematician cannot be judged as he left no mathematical publications but we know he wrote very stylish Latin! One might reasonably ask how someone who left behind no evidence of mathematical ability came to hold two of the major mathematical chairs in England. It appears mainly due to William Laud, archbishop of Canterbury (1633-45) and religious adviser to King Charles I. Laud became president of St John's, Oxford, in 1611 and then chancellor in 1629. Laud set up a committee which produced the Laudian statutes, new endowments and new buildings in Oxford. Turner was a highly active member of this committee and so came to Laud's notice. Through Laud, Turner gained the appointment to the Savilian chair of Geometry at Oxford. Wood writes in  that Turner was:-
... a most exact latinist and Grecian, was well skilled in the Hebrew and Arabic, was an accomplished mathematician, was excellently well read in the fathers and councils, a most curious critic, a politician, and what not ... He wrote many admirable things, but being too curious and critical, he could never finish them according to his mind, and therefore cancelled them ...Perhaps the fairest summing up is by Adamson  who describes Turner as:-
... more obviously a Royalist and an Anglican than an academic of any sort.
Article by: J J O'Connor and E F Robertson