Dickinson’s attachment to the Portland Whigs cost him his seat for Rye in 1790. He originally owed it to his wife’s family interest, but Thomas Lamb, manager of the borough, informed him, 11 June:
We should hope it will not be very displeasing to you to retire when the politics of the times run so contrary to your own; to attempt to accomplish your wishes soon with the assurances of your giving your support to government I found would be very hardly combated.
Lamb also rejected Dickinson’s offer to come in as locum tenens for his son Thomas Phillipps Lamb. To the latter Dickinson wrote that he would retire into private life as he could not represent Rye, to the former of his bearing his ‘great disappointment’ with ‘the most perfect resignation and good humour’. To the Duke of Portland he wrote that, as a victim of his loyalty to him, he had ‘a prior claim to anyone to regain that very seat ... or such other as I may approve of’. To ‘his Royal Highness’ he wrote that his being thrown out was a measure forced on his constituents and that he had ‘no doubt at a future opportunity of being reinstated’.
In August 1792 there was a vacancy for the county of Somerset, where Dickinson’s inherited wealth had been invested in a respectable estate. He was tempted to offer, with a hint of government support, of which his associate Hans Sloane warned him to be cautious owing to his past voting record. In the event, he made way for Henry Hippisley Coxe and Sloane congratulated him on not endangering a ‘constitution so sensible to fatigue’.
On 18 May 1796 Pitt was informed by James Grenville apropos of Dickinson, ‘I can answer, I think, for his orthodoxy’. He had evidently approved Portland’s line of junction with government.
Dickinson denied that the peace of Amiens posed a threat to commercial interests, 13 Dec. 1802. On 3 June 1803 he voted with Pitt and in March 1804 was reckoned, with his son, a supporter of Pitt in opposition to Addington. Their vote for Pitt’s naval motion confirmed it, 15 Mar., and on 16, 23 and 25 Apr. they both voted in the minorities that brought down Addington. With his son in office, he supported Pitt’s second ministry and was in the government minority on Melville’s case, 8 Apr. 1805. He ceased to draw attention to himself in debate. He was absent on the first major division after the formation of the Grenville ministry, 3 Mar., and died 25 May 1806. His ‘now only surviving’
