pointed by the commons to sit during the recess in the summer of 1641, and on 26 Oct. 1641 delivered a speech in support of the exclusion of the bishops from votes in parliament (Old Parliamentary History, x. 14). The king, finding he ‘did disserve him notoriously,’ proposed to appoint Hyde solicitor-general in his place, but Hyde refused, and it was not till 30 Oct. 1643 that Sir Thomas Gardiner superseded St. John (Clarendon, Rebellion, iv. 126, viii. 213; FOSS, vi. 480). When the king summoned St. John to follow him to York, the House of Commons refused him leave to go (Commons' Journals, ii. 600). They passed an ordinance enabling him to perform all the duties of the attorney-general, who had joined the king (28 May 1644), and also appointed him one of the six commissioners charged with the custody of the new great seal (10 Nov. 1643), which office he continued to hold till 30 Oct. 1646 (Husband, Ordinances, 1646, folio, pp. 385, 499).
During the civil war St. John came gradually to be regarded as one of the leaders of the independents. He delayed taking the Solemn League and Covenant as long as he could safely do so (Memoirs of the Verney Family, ii. 166). From the close of 1643 he and Vane were the heads of the war party in the lower house. Robert Baillie terms him ‘Mr. Pym's successor’ (Letters, ii. 133). In January 1644 he discovered and revealed Brook's plot for inducing the city to declare for peace (A Cunning Plot to divide and destroy the Parliament and the City of London, 4to, 1643). The original institution of the committee of both kingdoms, of which he was from the first a member (16 Feb. 1644), and the device by which the opposition of the lords to its renewal was frustrated were the work of St. John and Vane (Gardiner, Great Civil War, i. 304, 343; Baillie, ii. 141). St. John, who was an active member of the Westminster assembly, was at first regarded by the Scots as one of their strongest friends; but his share in passing the toleration order of 13 Sept. 1644 produced loud complaints from the presbyterians (ib. ii. 117, 145, 230, 235–7). In the later period of the Westminster assembly he was one of the ‘Erastian lawyers’ who obstructed the establishment of the presbyterian system by their insistence on the rights of the state.
St. John was one of the commissioners appointed to treat for a peace at Uxbridge in January 1645, but took little part in the debates (Gardiner, Great Civil War, ii. 121). He supported the self-denying ordinance, and helped to procure the exemption of Cromwell from its operation (Holles, Memoirs, ed. Maseres, pp. 209–14; Clarendon, Rebellion, viii. 261). A letter which St. John wrote to Cromwell in February 1646, about the lands conferred by parliament upon the latter, supplies a further proof of the political agreement which then existed between the two (Thurloe Papers, i. 75). In 1647, during the quarrel between the army and the parliament, St. John adhered to the army, though remaining rather in the background while the struggle lasted. He signed the engagement of 4 Aug. 1647, to support Fairfax against the city, and was a member of the committee appointed after the army's victory to examine into the late riots (Rushworth, vii. 755; Walker, History of Independency, i. 51, ed. 1661; Clarke Papers, i. 135, 158, 219, 231). St. John doubtless concurred in the vote for no further addresses to Charles I, although during the months which followed he, like Cromwell, made an attempt to open negotiations with the Prince of Wales, and even discussed the desirability of fresh overtures to the king (Gardiner, iii. 57; Hamilton Papers, Camden Society, i. 148, 174). Thus from 1644 to the beginning of 1648 he continually acted in harmony with Cromwell, and Holles gave voice to the general opinion, when in February 1648 he dedicated his memorial to ‘the unparalleled couple’ as being ‘the two grand designers of the ruin of three kingdoms.’ The enthusiastic letter which Cromwell addressed to St. John after his victory at Preston shows how complete his confidence in his associate was (Carlyle, Cromwell, Letter 67). Towards the end of 1648, however, St. John's policy began to diverge from Cromwell's. On 12 Oct. 1648 the commons appointed him chief justice of the common pleas, and on 22 Nov. following he was sworn in. He therefore abstained, in accordance with the usual custom, from attending parliament, took no part in the proceedings which brought Charles I to the block, and, though appointed one of the commissioners for the trial of the king, refused to act (Foss, vi. 481). In the vindication which he printed at the Restoration St. John protested that he had nothing to do with the king's death, Pride's Purge, or the establishment of the Commonwealth (The Case of Oliver St. John, 1660, 4to, pp. 5, 12; Thurloe Papers, vii. 914). His dissatisfaction was shown by the fact that, though a member of the council of state, he attended sixteen only out of 319 meetings during his first year of office. During the second year he attended forty-nine meetings. In June 1650, when Fairfax resigned command rather than invade Scotland, St. John was one of the committee appointed by parliament to satisfy him of the justice of
