Somerville was returned for his county in a by-election in 1800 on the independent interest, and at Westminster achieved the distinction of being the only Irish Member to vote with opposition for Grey’s amendment to the address, 2 Feb. 1801. The Castle duly labelled him ‘Opposition’ and he was thus distinguished by Lord Wycombe, 15 Jan. 1802, with reference to the Irish corps at Westminster: ‘Of the whole deputation Sir Marcus Somerville alone, if I mistake not, declines concurring in the vote which gives to that transcendent measure [i.e. the Union] the sanction of a parliamentary approval’. On 7 May 1802 he voted for a motion of thanks for the removal from office of Pitt. He voted for inquiry into the Prince of Wales’s finances, 4 Mar., and against the resumption of hostilities, 24 May 1803, and was apparently recruited from Ireland to vote as a friend of the Prince. His opposition was not particularly vocal, the only speech by him traced being a condemnation of the Irish duties, 20 June 1803, if nothing was to be done for Catholic relief.
Somerville, who was counted a supporter of the Grenville ministry and was believed by Fox to be ‘staunch’, puzzled the latter by his elusive absence in May 1806, despite the appeals of the chief secretary and Irish lord chancellor. On 9 June Fox informed the viceroy, ‘No one can tell where Sir Marcus Somerville is to be found’. Perhaps he was preparing the fête champêtre in honour of the Prince of Wales’s birthday held at Somerville on 12 Aug.
The Regency gradually brought about a volte face in Somerville’s politics. In the Parliament of 1812, while he invariably voted for Catholic relief, he appeared in no other opposition minority. In January 1815, in an interview with the viceroy, he stated his wish ‘to support the government and interest of the Prince Regent, from whom I have received marks of gracious consideration’, asking at the same time for legal office for his cousin Sir Henry Meredyth. Having ‘sent in his adhesion’, Somerville was certainly in the government divisions by 31 May 1815, and by 8 Mar. 1816 the chief secretary could assure the viceroy that Somerville had, since his ‘conversion’ given ‘a regular and very efficient support as far as attendance goes’. He added that Somerville ‘has hitherto received no favour from us whatever, but has expressed no kind of dissatisfaction—indeed, quite the contrary ... He is perhaps the best attendant we have.’
