Having renounced a career in the church in accordance with the wish of his benefactor Isaac Gardiner that he should become ‘a country gentleman’, Fynes was engaged in classical studies when the 4th Duke of Newcastle, another distant relative, invited him to come in for Aldborough. After the election he wrote: ‘There could not be at that moment in the whole kingdom one more astonished at finding himself called to the duties of a Member of Parliament or more unprepared and unqualified for such a situation’.
His ‘natural reserve’ made Fynes reluctant to speak in debate. ‘There was always something which had as yet escaped my observation, and which was nevertheless necessary for the discussion of the subject; when therefore I could not have satisfied myself, how could I expect to have satisfied others?’ Grief at his wife’s death in premature childbirth drove him back to his literary pursuits for much of 1810 and during his absence he was classed as ‘doubtful’ by the opposition. He resumed attendance towards the end of the year and supported Perceval in the Regency debates. Later he declared ‘Among public men, Mr Perceval was the only individual of whom I had any intimate knowledge and from whom I might have derived countenance or encouragement, and he was snatched away’. On 20 May 1812 he took a month’s leave of the House.
After Perceval’s death Fynes gave up any idea of parliamentary eminence. His inheritance from Isaac Gardiner gave him financial security and his remarriage brought him back into social life. In 1812 he bought Welwyn House. He attended Parliament only on questions of special importance. He was listed as a government supporter after the election of 1812. He opposed Catholic relief in May 1813, in 1816 and 1817. But he voted for the reduction of army estimates, 6 Mar., against the property tax, 18 Mar., and the Bank restriction bill, 3 May, and for the economy motions of 3 Apr., 6, 7 May 1816. He rallied to ministers on the suspension of habeas corpus and its consequences, 23 June 1817, 5 Mar. 1818, and on the ducal marriage grants, 15 Apr. On 15 Jan. 1819 he wrote in his journal:
Being now sworn in as a Member of the House of Commons for the fourth time, I was mortified at perceiving that I never could be capable of acting a part in public life. I felt that I was out of my place and engaged in a department for which I was not fitted. But I consoled myself with the consideration that I might become a writer.
On 18 May 1819 he voted against Tierney’s censure motion. A fortnight later his patron sent for him and proposed that he should speak in the financial debates of 6-7 June, thus making himself ‘known to the ministers and useful to them’: this was to be a stepping stone to office in one of the finance departments. He refused: ‘as to the higher official situations I am convinced that I am not fit for them, and as to the lower offices, they are not fit for me’. He resumed attendance in November 1819.
Fynes retired from Parliament in 1826, admitting that he had been ‘an inefficient Member’. The rest of his life he devoted to the preparation of his Fasti Hellenici and Fasti Romani and other classical enterprises.