Digby, and defended by his kinsman, Sir Kenelm, were afterwards published in 1651. On one of his short occasional visits to London, Digby quarrelled with a gentleman of the court, whom he wounded and disarmed within the precincts of the palace of Whitehall. For this offence he was imprisoned and treated with considerable severity. Upon his release he vowed vengeance against the court for the indignities which he had suffered. His opportunity soon came, for in March 1640 he was elected as one of the members for the county of Dorset, and was again returned for the same constituency at the general election which occurred a few months afterwards. On 9 Nov. 1640 he moved for a select committee to draw up a remonstrance to the king on ‘the deplorable state of this his kingdom’ (Parl. History, ii. cols. 651–4), and on 11 Nov. he was appointed a member of the committee instructed to undertake the impeachment of the Earl of Strafford. Though at first very eager in prosecuting the charges against the unfortunate earl, Digby gradually changed his tactics, and at length, on 21 April 1641, he vigorously opposed the third reading of the Attainder Bill (ib. cols. 750–4). His speech gave great offence to those with whom he had been lately acting, and on the next day he was called upon to explain. No further proceedings were then taken, but the speech having been afterwards printed, the House of Commons on 13 July ordered that it should be publicly burnt by the common hangman (ib. col. 883). Many months afterwards appeared ‘Lord Digbie's Apologie for Himselfe, Published the fourth of January, Ann. Dom. 1642,’ in which he affirmed that Sir Lewis Dive had given the directions for printing this speech without asking his consent. Meanwhile on 9 June 1641 Digby was called up to the House of Lords in his father's barony of Digby, and took his seat on the following day. Much was expected from his accession to the court party at this critical period; but his restless disposition and untrustworthy character prevented him from being of real use to any party in the state. Though he had himself urged the prosecution of the five members upon the king, he actually whispered into Lord Kimbolton's ear, while sitting next to him in the House of Lords, that ‘the king was very mischievously advised; and that it should go very hard but he would know whence that counsel proceeded; in order to which, and to prevent further mischief, he would go immediately to his majesty’ (Clarendon, Hist. of the Rebellion, i. 508). Furthermore, upon the retreat of the five members and Lord Kimbolton to the city, Digby suggested that they should be followed and seized by armed force. Though his proposal was rejected by the king, it soon got to be generally known, and Digby became one of the most unpopular men in the country. One day in the beginning of January 1642 he went to Kingston-upon-Thames upon business for the king ‘in a coach with six horses, and no other equipage with him, save only a servant riding by him, and a companion in a coach’ (Wood, Athenæ Oxon. iii. col. 1101). Wood's account of this journey, however, materially differs from that received by parliament. It was asserted that Digby and Colonel Lundsford had collected some troops of horse, and had appeared in arms at Kingston. Digby was ordered to attend in his place in the House of Lords to answer for himself, and Lundsford was committed to the Tower. Instead of obeying the summons, Digby fled to Holland, and on 26 Feb. 1642 was impeached of high treason in the House of Commons (Parl. History, ii. cols. 1103–5). Owing, however, to the confusion of the times, the prosecution of the impeachment was not carried through.
Unable to remain quietly in Holland, Digby came over to York, where he stayed some days in disguise. Upon his return voyage he was captured by one of the parliamentary cruisers, and taken to Hull. There he made himself known to Sir John Hotham, the governor, whom he attempted to gain over to the royal cause. Though Hotham refused to be persuaded to desert his party, he connived at Digby's escape. Upon the breaking out of the civil war, Digby took part in the battle of Edgehill. He greatly distinguished himself by his gallantry at the taking of Lichfield, and was shot through the thigh while leading an assault upon that city. Falling out with Prince Rupert soon afterwards, Digby threw up his command, and returned to the court, which was then at Oxford. On 28 Sept. 1643 he was appointed by the king one of the principal secretaries of state in place of Lord Falkland, and on the same day was admitted to the privy council. On the last day of the following month he became high steward of Oxford University, in the room of William Lord Say, who had been removed on account of his adherence to the parliament. Digby's conduct of affairs as secretary of state was both unfortunate and imprudent. His visionary project for a treaty between the king and the city of London was quickly frustrated by the interception of Digby's letter to Sir Basil Brooke. His lengthy negotiations with Major-general Sir Richard Brown for the betrayal of Abingdon terminated in his utter discomfiture, while his correspondence with Lesley and the other commanders of the Scotch army in England