Euston’s father, as chancellor of the university, had assisted in his and William Pitt’s joint triumph at Cambridge in 1784. Thereafter Euston retained the seat as Pitt’s adherent, though alleged to be ‘in danger’ in the contest of 1790.
Euston had made no mark in Parliament. On 18 Apr. 1791 he voted for the abolition of the slave trade, to which he was a ‘staunch friend’ in 1806. He was at the head of the delegation of Members who congratulated the Duke of York on his marriage, 1 Feb. 1792. He voted with ministers on the loyalty loan, 1 June 1797, and for the assessed taxes, 4 Jan. 1798. He was consulted on militia policy and in 1798 went to Ireland with his regiment: while he was there Buckingham again suggested his fitness to be viceroy, but dismissed his military pretensions. The King, on the other hand, thought highly of his militia exertions.
Euston followed Pitt’s line in supporting the Addington ministry. He was a steward at Pitt’s birthday dinner, 28 May 1802. On 22 Feb. 1803 he moved an address of congratulation to the King on his escape from the alleged plot against his life. The business of the Queensferry election committee, the usefulness of shorthand writers in committees and the residence of the clergy were his only other subjects that session. On 1 Mar. 1804 he informed his father that he proposed joining Pitt in his and Fox’s opposition to the ministry and would, as soon as the King had recovered from his illness, resign his place.
On Pitt’s return to power, Euston might have had the pay office or the mint, but elected to retain the rangership. There were rumours of a peerage. He assured Pitt, 12 May,
that the vote in Parliament of any man who shows himself not greedy of the emoluments of office is more worth having at all times and may be of more use at critical periods than double the number given by persons who have not had an opportunity of making this point perfectly clear.
He had warned Pitt the week before of the danger of returning to office ‘feebly instead of powerfully’, as a result of Eldon or Addington poisoning the King’s mind against ‘the extended scheme of government’ which, like Pitt, he had thought preferable, and of stirring up ‘an opposition of talents’. Euston’s father also favoured a broad-bottomed administration.
Subsequent events confirmed Euston’s initial disappointment with Pitt’s second ministry. Pitt turned his brother-in-law John Smyth out of office (with an apology to Euston); was reconciled with Addington, which he could not stomach; and produced a militia enlistment bill about which he had private misgivings, though he defended it in the House, 26 Mar. 1805.
On Pitt’s death, Euston urged his friends to apply for parliamentary payment of his debts. He was one of the six assistant mourners at the funeral. Meanwhile, despite initial misgivings, he had at his father’s instigation come to terms with the Grenville ministry. Writing to Lord Grenville on 18 Feb. 1806, he surmised that his being retained in his place was on the supposition of his support. This was ‘perfectly well founded’, but he reserved the right to endorse the measures promoted by Pitt. He received a reassuring answer, hoping for his ‘good opinion and friendship’. The test came on 30 Apr., when the House divided on the repeal of Pitt’s Additional Force Act. He voted for repeal and evidently sought to justify his vote, though the reporter claimed that he spoke too low to be heard and understood him to speak in the opposite sense. His memorandum ‘Reasons for the political conduct of an individual’, dated 5 June 1806, justified his conduct by reference to Pitt’s wishes for a junction with Grenville and Fox the year before, and to the political reconciliation with his father that it entailed. By October he was regarded as a turncoat by the Pittites in opposition. That month Lord Albemarle failed to persuade him to exchange places, when he no longer wished to be master of buckhounds.
On 23 Mar. 1807 Euston presented a university petition against the Catholic bill; but he remained loyal to the outgoing Whig ministry, resigning office with them and voting for Brand’s motion on 9 Apr. He went on to vote with them against the address, 26 June, and for Whitbread’s censure motion, 6 July 1807. This put paid to any notion that he would support the Portland ministry, which rashly claimed credit for his heading the poll in the contest for the university.