Arden, a lord of the Admiralty in Pitt’s administration, had to look for another seat in 1790, his erstwhile patron the 2nd Duke of Northumberland having deviated from Pitt. He was found one on Lord Warwick’s interest. Soon afterwards he was re-elected on his appointment as registrar of the court of Admiralty, an office to which he had held the reversion since 1764. In 1798 it netted him in fees over £8,000.
Arden subsequently figured largely as the champion of his younger brother Spencer Perceval, chancellor of the Exchequer from 1807 and prime minister from 1809 until 1812. He had always been his provider and confidant; they had married sisters. Early in 1807, Arden was go-between for Lord Sidmouth with his brother when Sidmouth contemplated concerted opposition to the Catholic bill. The brothers’ solidarity was put to the test by opposition attacks on Arden’s Admiralty sinecure, to which his brother had the reversion. The Whig chancellor Lord Henry Petty had pointed out in February 1807 that it was one of two substantial English places held in reversion that had escaped abolition. As a peer Arden thwarted Henry Bankes’s bid to abolish reversions, 4 Aug. 1807, by reference to the royal prerogative and, when the Commons sent it back in March 1808, again led the successful opposition to it, evoking the conflict of 1641. This was in defiance of the ministry, who sought a compromise and consented to a suspension of grants in reversion, but further attempts by Bankes to make the Lords swallow abolition were frustrated: he had to be satisfied with a temporary suspension act (1812).