Thornton’s family embarked on their career as merchant princes at Hull, which he represented in Parliament for 22 years, being first returned with his cousin William Wilberforce. By 1788 his interest there was regarded as established, thanks to his commercial concerns (Crosse Co.) and his influence with the dissenters and Methodists. In 1790 his compromise with the Whig interest averted a contest and no mention was made of politics. His own were expected to be to ‘go with the ministry for the time being’.
On the death of his father, worth about £600,000, in 1790, Thornton became head of the family business trading to the Baltic;
As a Bank director, Thornton could usually be relied on to speak up, even if his colleagues were silent in the House. On other subjects he was less forthcoming. Allowance must be made for confusion in the attribution of speeches between him and his brothers, but he was certainly not as ready in debate as Henry and spoke less regularly than either Henry or Robert. On 21 Mar. 1791 he criticized frauds arising out of the drawback on sugar. Pitt reported him as speaking in favour of his Russian policy, 29 Mar. 1791, but the reporters ignored it.
every year during the war we should make an offer of peace to the enemy, provided they should be disposed to remove the grounds of war. What had displeased him in the language of ministers was, that they seemed to hold out no other termination of the war than the destruction of the present French government, an object which he believed could never be effected by force of arms. Now that the question was decided to carry on the war, he was ready to oppose it.
Yet he did not join his brothers and other ‘Saints’ in dividing against Pitt. Later that year he was one of the promoters of the City merchants’ declaration of loyalty to government.
In defence of the London wet dock, Thornton cited the example of Hull, 16 May 1796, admitting that the scheme had at first been unpopular there. He was not so popular himself at the ensuing election, needing help to take second place in the poll. A proposal that the poor should eat barley during the scarcity of wheat was attributed to him by his critics, but denied. On 17 Mar. 1800 he moved a bounty on the importation of wheat from the Baltic. He contributed £20,000 to the loyalty loan for 1797. He voted for Pitt’s assessed taxes, 4 Jan. 1798, was teller for the land tax bill, 4 Apr., and was critical of his fiscal measures only in so far as they affected the East India Company, 25 Apr. 1798. Privately he approved of the income tax as ‘highly advantageous to the State’.
Thornton was more partial to Pitt than to any other minister and he was surely the ‘Mr Thornton’ who on 7 May 1802 seconded Belgrave’s vote of thanks to him, expressing approbation of his financial measures in the preceding decade. He was a member of the committee on the Prince of Wales’s duchy revenues, 17 Feb. 1802, but had little to say in debate during Addington’s ministry. A speech of 3 June 1802 suggests that he had polite reservations about the premier’s financial policy. He headed the poll at Hull, where the dock had proved a success. ‘Nothing could stand against the weight of administration joined to the three corporations in favour of Mr Thornton.’ He informed Charles Long in April 1803 that City opinion was in favour of Pitt’s resuming the helm, but excluding Lord Grenville; yet he did not join Pitt in opposition to Addington until 15 Mar. 1804. He went on to vote with the minorities that forced the ministry to resign, 23, 25 Apr. 1804. He was listed as Pitt’s adherent in March and September 1804 and again in July 1805, though he had joined in the vote against Melville on 8 Apr. and was chosen for the select committee on the tenth naval report on 25 Apr. He wrote to Pitt on 10 Apr.:
I trust you will give me credit in assuring you that an imperious sense of duty in our view of the matter compelled my brothers and me to give our support to Mr Whitbread’s motion.
I wish to inform you that having by that vote expressed my opinion of the facts disclosed by the report of naval enquiry I shall support any motion that may be made to give Lord Melville an opportunity of showing he had no participation with Mr Trotter.
Glenbervie Diaries, i. 181; Wentworth Woodhouse mun. F36/20; PRO, Dacres Adams mss 4/93, 6/42.
Accordingly, he opposed Whitbread’s motion of that day for Melville’s dismissal, refusing to believe he was ‘guilty of personal corruption’, as he was ‘an active, zealous and meritorious servant of the public’, who had been sufficiently punished by censure. On 14 June he went on to exonerate Pitt from any blame in his dealings with Boyd & Co., a subject on which he had given evidence to the commissioners for their tenth report on 8 May.
On Pitt’s death, Thornton was prepared to promote a private subscription to pay his debts, but George Rose thought him ‘cool’. On 7 Mar. the bishop of Lincoln informed Rose, ‘I know that Mr Samuel Thornton told Lord Grenville very early that he meant to support’. He was in opposition that session only on the American intercourse bill, 17 June; and Grenville was reluctant to overlook Thornton in favour of his cabinet colleague Earl Fitzwilliam over a piece of Hull patronage. Thornton himself assured Fitzwilliam, whose support he courted, 25 Oct. 1806, ‘it is the intention of my family now likely to possess four seats to give the present administration a general and fair support which is as much as we have done to any government’. But to his mortification he was defeated at Hull. He might have come in for Surrey, where he had become a country gentleman through the purchase of the Albury estate in 1800, but having been put up without his knowledge, declined while in second place rather than displace the bona fide candidates, one of whom was opposed to the abolition of the slave trade. He nevertheless staked his claim for the next election and in 1807 defeated Lord William Russell, who was sure that Thornton was a ministerial nominee. He himself admitted his leaning to government, ‘without attaching myself to any party that may prevent my giving an unbiased, as I trust it will always be a disinterested vote on any measures that may arise’.
Thornton opposed Folkestone’s motion for the restoration of the Danish fleet, 29 Mar. 1808, denying the necessity for any declaration of intent about it. He was in two minorities against the Duke of York, 17 Mar. 1809, taking the line of the ‘Saints’. But he approved the formation of Perceval’s ministry
Thornton did not seek re-election in 1812. For several years he had been in financial difficulties. His house lost £50,000 through the failure of the house of Watson of Preston. The depressed state of the Baltic trade brought his London house to a temporary halt in 1810 when he was seeking a licence to export to Russia, assuring ministers of the Tsar’s goodwill towards them. He retained his Hull interests. In 1811 when he sold Albury for £72,000, there were stories of his being in hot water for exporting bullion; it was already known that he meant to give up the county seat. On a vacancy late in 1813 Thornton resumed it, though he was prepared to give the first option to William Joseph Denison.
Faced with a contest for Surrey in 1818, Thornton retired, out of regard for his colleague Sumner. He made no attempt to re-enter Parliament. His commercial and evangelical heritage had been modified by his family pride and genteel ambitions.