Anstruther had made his reputation as a powerful opposition speaker in the House, specializing in Indian affairs and legal issues. He joined the Whig Club, 17 Jan. 1785, and Brooks’s, 5 Mar. 1788. He attacked Henry Dundas at every opportunity, both in and out of the House, which made his seat for the family burghs precarious, his father having had to ally himself with Dundas to overpower opposition. His parents had hoped that this alliance would lead to professional promotion for Anstruther, who was reported to be going out to India; but nothing came of it and in 1789 Dundas refused to countenance Sir John Anstruther’s returning his son at the next election. To avoid martyrdom, as Anstruther called it, he looked for a seat elsewhere. After an unsuccessful application to the Duke of Queensberry, and an equally unsuccessful contest at Pontefract, he obtained a seat, by Lord Loughborough’s mediation, for Cockermouth, where Lord Lowther, the patron, gave him preference over a friend of his own.
Anstruther continued to act with opposition until 1792. As a manager of Warren Hastings’s impeachment, he supported its continuation, 17 Dec. 1790, a line of which he never repented subsequently. He was a critic of the armament against Russia, 15 Apr. 1791, and both then and on 1 Mar. 1792 voted against Pitt’s policy. He predictably supported the exemption of Scotland from the Test Act, 10 May 1791. He deprecated Burke’s alarm about French revolutionary principles, 6 May 1791, though, consistently with his previous views, he opposed Scottish burgh reform, 27 May 1791, 5 and 18 Apr. 1792. On the latter occasion he
professed himself entirely against the motion, as a point of vain, vague and speculative theory, that could not be reduced to practice. He was convinced that the more the practice of the constitution of England was looked into and compared with the visionary theory of other people, the more would it be admired.
Anstruther was a critic of the war against Tipu in India 15 Mar. 1792, and was about to make a motion against the breach of faith with the nawab of the Carnatic—regarded as a possible rallying point for the divided opposition—when the need for action against sedition in May drew him into the camp of the Whig alarmists. On 25 May he accepted the royal proclamation as a bulwark against ‘levelling’ principles and rallied to the protection of the constitution. In November he was one of the conservative Whig junta. To his friend William Adam, who preferred Fox’s political line, he wrote:
I trust in God that any political difference can be but temporary and that in all events upon other points our friendship will continue what it ever was. We do not differ, I am sure, on principle; we differ upon a fact: the danger of the country. This necessarily leads to difference on the means of averting it. Both, I am sure, equally actuated by good motives.
To the like-minded William Windham he wrote, 30 Nov., that he was reconciled to a ‘decided difference with Fox’, not being able to stomach a ‘violent and hostile opposition’. On the address, 13 Dec., he argued that ministers, ‘so far from exciting a premature or groundless alarm, had rather been too late in adopting their measures of precaution’, and on 1 Feb. 1793, viewing the execution of Louis XVI ‘with the utmost horror’, he was prepared for war owing to ‘the infinite danger to be apprehended from the propagation of French principles’. That month he was a conspicuous member of the ‘third party’ meeting at Windham’s house which resolved to support the government in time of war, and he seceded from the Whig Club.
Anstruther’s political volte face had gained him, apart from a Welsh judgeship and the unsalaried post of counsel to the Board of Control, the appointment of solicitor-general to the Prince of Wales. As such he helped draft, and vindicated in the House, the bill for the redemption of the Prince’s debts in 1795. By insisting, however, that the duchy of Cornwall revenues were not the Prince’s by right, he incurred the latter’s displeasure and, after a public rebuke by Sheridan on behalf of the Prince, he was dropped by him.
Anstruther was restored to his seat for the family burghs with Dundas’s blessing in 1796. He disliked the pacific tone of the new Parliament, advising Dundas to promote a scheme of home defence to revive a warlike stance towards France. He attended until June 1797 when he was appointed chief justice of Bengal, a post he had hoped for seven years before. In March 1795 he had applied to Dundas to become governor-general of Madras. Pitt acquiesced in his proposal to stay five years, instead of the usual seven, but this was frustrated by a Lords’ amendment. So, at first, was Dundas’s bid to get him a baronetcy, which the King refused: but he subsequently relented.
Since his arrival, British justice has really appeared in genuine purity and lustre in this quarter of the globe, and a degree of respect and confidence has attended the character of his Majesty’s judges in all their decisions, which has greatly elevated the national honour in this settlement ... it is my conscientious opinion that no judge ever sat upon the bench in any country with more honour to the authority represented, or with more advantage to the public.
Hickey Mems. ed. Spencer, iv. 230, 388; Sidmouth mss; Blair Adam mss, Anstruther to Adam, 21 Feb., 26 Mar., 4 June, 20 July, 6 Aug., 4 Oct. 1802, 8 June 1804.
Anstruther secured his pension by William Adam’s mediation with Pitt’s second ministry, and arrived home in July 1806 to find Lord Grenville in power.
Anstruther was at once courted by the Grenville ministry, Wellesley assuring the premier that he was ‘very well disposed, and you will find his conduct very satisfactory’. The bait was the offer of undertaking the judicial business of the Privy Council in the absence of the master of the rolls, offered by Grenville through Wellesley. Anstruther, after some hesitation, elected to accept the management in the Commons of Privy Council business. He was made a Councillor and came into Parliament again on the family interest, though he maintained that, given a little more time, he might have come in for the county of Fife.
Anstruther’s most conspicuous parliamentary activity at this time was the defence of Wellesley against charges of misconduct in India: between January 1807 and March 1808 he made a series of speeches in Wellesley’s favour, carrying his exoneration on the Oudh charge, 15 Mar. 1808. He was also a member of the East India committee in 1808, 1809 and 1811 and made it clear there and in debate that he did not wish to see Company rule undermined. (Francis Horner indignantly described his role as that of ‘a commonplace jobber and Scotchman’.)
In June 1809 the Portland administration offered Anstruther the chair of the India Board. He refused, but was reported to have regretted this decision. On 14 July he assured Robert Saunders Dundas that he was at the call of government ‘upon Indian subjects’. By 25 Sept., however, he doubted whether he could serve the government as then constituted, by 1 Oct. despaired of them, and feared by 5 Oct. that ‘the Jacobins will overset us all’. When Wellesley took office under Perceval that month, he pressed for a place for Anstruther, ‘if he should be desirous as I trust he will be of supporting the King on the present occasion’. But Anstruther had already refused Perceval’s offer of the India Board, explaining to Grenville, whose refusal to parley with ministers he approved, that he would prefer to see a union of ‘all the talents’ and ‘all the respectability of character’ of the country in power. He added that it was only on Catholic relief, to which he was indifferent, that he appeared to differ from Grenville; as for Wellesley, in parting company with Grenville, he had broken ‘the closest possible intimacy’ with Anstruther. Wellesley failed to induce Anstruther to change his mind and rally to government.
When Grenville was cabinet making at the outset of the Regency, Anstruther declined a place at the Board of Control, pointing out that he had grown accustomed to refusing the chair, but added ‘if without office I can execute the office of president of the Board of Trade or vice-president you may command my services’. He had voted staunchly with opposition during the Regency debates and also appeared in the minority against the Irish chief secretary’s anti-Catholic circular, 22 Feb. 1811, but could not bring himself to support the opposition censure of the chief secretary on 8 Mar.