Although his father was a prominent Pittite, Smyth formed Whig friendships at university, where he carried off the classical prizes, notably with Lord Henry Petty. In 1802 his father thought of putting him up with himself at Pontefract, but he had to be content with canvassing for him.
I have only to say that what has suggested itself to you respecting my son, affords an opportunity for your kindness towards me, which will be gratefully received. I should be very glad to have him trained to business in a line suitable to his pretensions. I have heard that the office of under-secretary of state in Lord Hawkesbury’s office, having been declined by the person to whom it was offered, is not filled up, and if you could do me the favour to recommend him to it, it would be a most desirable situation for him, and a strong proof of the continuance of your regard to me, which to have forfeited would be I do assure you the most sensible mortification I could receive in life.
Smyth duly became under-secretary at the Home Office until Pitt’s death. On 14 Oct. 1806 he pointed out to Petty:
my appointment was entirely owing to Mr Pitt, and although I felt that it imposed upon me a duty with respect to the government while it subsisted, yet I neither had then, nor have I, any obligation to Lord Hawkesbury further than what is due for his personal civility and kindness to me during the time of my connection with him.
He still had no seat in Parliament. His father had applied unsuccessfully to Pitt on 27 Dec. 1805 for the vacant seat at Boroughbridge:
The wish I feel to see him in Parliament will I hope excuse my mentioning it to you again, after the very obliging manner in which you expressed yourself upon it last year and I will only add that it will be a very great additional obligation conferred upon me.
Smyth’s friends in power did not seat him either, though on 21 Apr. 1807 Lord Grenville, then out of office, recommended him to Lord Caledon as a man who would ‘do credit to any person by whom he is brought forward’.
In 1811 Smyth’s uncle became 4th Duke of Grafton and put him up for the seat for Cambridge University which he was vacating. Smyth, the Whig candidate, was defeated by Lord Palmerston. Shortly before the dissolution he was returned unopposed on another vacancy and retained the seat for life. His obituary stated that ‘he courted neither party and the votes which he gave were dictated by his conscience’.
He died 20 Oct. 1822: ‘to a high reputation as a scholar, he united great suavity of manner and kindness of heart’.
