Chaderton resigned on 25 Sept.; contrary to statute, the vacancy was not announced, on the plea that all the fellows were in residence; the election took place on 2 Oct. with locked gates, and nothing was known of it at Queens' until Preston was sent for to be admitted as master of Emmanuel. The statutes limited the master's absence to a month in every quarter. This would interfere with Preston's preaching at Lincoln's Inn. His ingenuity found out evasions to which the fellows consented; the statutes condoned absence in case of 'violent detention' and of 'college business;' a 'moral violence' was held to satisfy the former condition, and a suit at law about a college living, which lasted some years, formed a colourable pretext for alleging college business. But Preston was inflexible on the point of vacating fellowships. In 1623 he was made D.D. by royal mandate. According to Ball, he had been selected by Buckingham to accompany Arthur Chichester, lord Chichester [q. v.], on a projected embassy to Germany, and was, on this occasion, made D.D. There is probably some confusion here: Chichester's actual expedition to the palatinate was in May-September 1622.
Preston was anxious for opportunities of preaching at Cambridge, and listened to proposals in 1624 for putting him into a vacant lectureship at Trinity Church. The other candidate, Middlethwait, fellow of Sidney Sussex, was favoured by Nicholas Felton [q. v.], bishop of Ely. The matter was referred to James I, who wanted to keep Preston out of a Cambridge pulpit, and, through Edward Conway (afterwards Viscount Conway) [q. v.], offered him any other preferment at his choice. It was then that Buckingham told Preston he might have the bishopric of Gloucester, vacant by the death of Miles Smith (d. 20 Oct. 1624). But Preston, backed by the townsmen, maintained his ground and got the lectureship.
He was in attendance as Charles's chaplain at Theobalds on Sunday, 27 March 1625, when James I died, and accompanied Charles and Buckingham to Whitehall, where the public proclamation of Charles's accession was made. For the moment it seemed as if Preston was destined to play an important part in politics. He exerted influence on behalf of his puritan friends, obtaining a general preaching license (20 June 1625) for Arthur Hildersam [q. v.] But he found his plans counteracted by Laud. On the plea of a danger of the plague, he closed his college and took a journey into the west. He wanted to consult Davenant at Salisbury about the 'Appello Cæsarem' of Richard Montagu or Mountague [q. v.], on which Buckingham had asked his judgment. From Salisbury he went on to Dorchester, and thence to Plymouth, where Charles and Buckingham were. When the news reached Plymouth of the disaster at Rochelle (16 Sept. 1625), Preston did his best to excuse and defend Buckingham against the outburst of protestant indignation. On the removal of Williams from the lord-keepership (30 Oct. 1625), Buckingham 'went so farr as to nominate' Preston to be lord keeper. Thomas Coventry, lord Coventry [q. v.], who had been counsel for Emmanuel College in the suit above mentioned, was eventually appointed.
Preston, however, could not draw the puritans to the side of Buckingham, whom they profoundly distrusted. Preston's friends urged the necessity of a conference on Montagu's books, and nominated on the one side John Buckeridge [q. v.], bishop of Rochester, and Francis White, then dean of Carlisle; on the other, Thomas Morton (1564-1659) [q. v.], then bishop of Coventry and Lichfield, and Preston. Buckingham played a double part, begging Preston as his friend to decline the conference, and letting others know that he had done with Preston. The conference was held in February 1626 at York House. Preston refused to take part, but came in after it was begun and sat by as a hearer. A second conference followed in the same month, at which Preston took the lead against Montagu and White.
Buckingham was elected chancellor of Cambridge University on 1 June 1626. Preston did not oppose his election, as Joseph Mead [q. v.] and others did; but he now felt his position in the university insecure, looked to Lincoln's Inn as a refuge in case he were ousted from Cambridge, and as a last resort contemplated a migration to Basle. A private letter to a member of parliament, in which Preston suggested a line of opposition to Buckingham, came by an accident into Buckingham's hands. Seeing that Preston's influence at court was waning, the fellows of Emmanuel petitioned the king to annul the statute limiting the tenure of their fellowships. Buckingham supported their plea. Preston had the support of Sir Henry Mildmay [q. v.], the founder's grandson. At length a compromise was reached. Charles suspended the statute (5 May 1627) till such time as six new livings of 100l. a year should be annexed to the college. Buckingham was now engaged with his ill-fated expedition (27 June 1627) to the Isle of Ré. In November Preston preached before Charles at Whitehall a sermon which was regarded as prophetic when,