Mahon reacted violently against the strictly radical education imposed on him by his eccentric father. On 4 Apr. 1800 he informed his half-sister Lady Hester Stanhope that he must throw himself on her uncle the prime minister Pitt’s protection, for ‘as long as I continue to exist ... so long will I continue in steady and determined opposition to Jacobin principles’. He wondered whether his father might be certified insane. His wish then was for a military career, but when Lady Hester engineered his escape from home in 1801, it was to a German university. On his return Pitt took up his cause against his father’s exploitation of his entailed estates and granted him a place worth £500 p.a., in his gift as warden of the Cinque Ports. Under Pitt’s aegis he further improved his prospects by marrying Lord Carrington’s daughter, with £20,000, in 1803.
On Pitt’s return to power in 1804, the exclusion of his father-in-law’s friend Lord Grenville tested his loyalties; and he was reported to have told Lady Fortescue, Grenville’s sister, that ‘he should not act with Mr Pitt but with Lord Grenville’. Her reply was that ‘he would do well to adhere to Mr Pitt, for that they had hangers on enough, like him, already’. Wilberforce, meeting him at this time noted, ‘Mahon seems well disposed and independent in mind and ways of thinking. I am mistaken if he keeps in the beaten track, and gives up his free agency to the degree it is done, alas, by the men of the world.’ Lady Hester Stanhope, as Pitt’s housekeeper, continued to obtain for Mahon her uncle’s favour. On 8 Mar. 1805 she applied for him to be appointed governor of Fort Charles, Jamaica, not so much for his own sake, as Pitt had already acted handsomely by him, as for his two younger brothers’. A place in Ireland fell into his lap instead. Lady Hester never forgave him for deserting Pitt’s friends at his death and adhering, with Lord Carrington, to Lord Grenville, who gave him another place.
On the day of Mr Pitt’s death, Lord Carrington ... went to Mr Rose and desired to know when the first payment would become due of a place given by Mr Pitt to Lord Mahon. Rose disgusted at this want of feeling for such a friend as Mr Pitt had been to him (Lord Carrington) ... told his servant to direct his lordship to a person more fit to give an answer to such a question than he was.
Life of Wilberforce (1838), iii. 186; Dacres Adams mss 9/65; Lady Hester Stanhope, 352; Farington, v. 72.
Mahon entered Parliament for Carrington’s borough of Wendover at the election of 1806. Lady Hester commented to Lord Melville:
Mahon ... is brought in by his shabby father-in-law, to expose himself in public as much as he has disgraced himself in private by his political opinions. I am quite ashamed of him, and do not allow him to come near me.
SRO GD51/1/201/1.
On 10 Feb. 1807 he was named to the select committee on finance. A staunch supporter of the abolition of the slave trade, he advocated it in his maiden speech, 23 Feb. 1807, in which he eulogized Pitt and suggested that the abolition might bring the country into greater favour with ‘that Supreme Disposer of events in whose hands victory is placed’. On 4 Mar. he went on to support the maintenance of Maynooth, the Catholic seminary, as ‘a great act of national policy’. He voted for Brand’s motion following the dismissal of the ministry, 9 Apr. 1807.
Mahon was returned both for Wendover and Hull in 1807, his father-in-law investing £3,000 in his return for the latter, which was uncontested.
Mahon’s subsequent conduct bore out this suggestion of disillusionment. In the session of 1811 only one vote, for Catholic relief on 31 May, is known. In September report had it that ‘Lord Mahon has made a promise to Lord Carrington not to go abroad, which is the only circumstance that would have led to his not wishing to be in Parliament’.
Mahon was put up in absentia for Hull in the election of 1812 at Lord Carrington’s instigation, but defeated. Carrington returned him on a vacancy for Midhurst before the year was out. It seems, however, that he preferred life abroad, for only one vote—again for Catholic relief, 30 May 1815—attests to his attendance in that Parliament before he succeeded to the title. At the time he was in Vienna. Francis Horner wrote of him, 10 Jan. 1817:
Mahon is of an affectionate temper, and his character is not without softness naturally; but he has no head, and I am told is lately become suspicious. That had not come upon him, when I knew him, but I should have said at that time that though one never could make any way with his understanding against an opinion he had once taken, he was equally susceptible of benevolent impressions as of the contrary and where he liked, was confiding and sanguine. I do not know of late years what the circumstances of his life have been, probably not so favourable for the blood he was born with, as the situation in which I used to see him.
Except on the Catholic question and not inconsistently with the line taken by his connexions, he became staunchly conservative as a peer.
