In 1774, his father's old friend (and first cousin twice removed), Lord Rockingham, offered Sondes a seat in Parliament for Lewis at Pontefract; however, Sondes declined due to the price of £3,500 asked by the borough's patron, Lord Galway. In 1775, the death of Sir Charles Saunders left a vacancy at Hedon. Rockingham did not wish to lose the seat to the Government, and recommended Watson as a candidate to Saunders' election manager, William Iveson, who had inherited Saunders' interest in the borough. However, the by-election in January 1776 was contested by Christopher Atkinson, and proved unexpectedly expensive; Sondes paid £3,600 and complained to Rockingham when bills came for a further £1,200 later in the year.[1]
Watson was a faithful member of Rockingham's opposition to the North ministry, but never spoke in the Commons. He put himself forth as a candidate for Kent in 1780 but withdrew on finding that he was not supported in the county.[1] At the 1784 election, he stood for Seaford on the long-dormant Pelham interest against the Treasury candidates. Defeated by one vote, he lodged an election petition holding that the bailiff had not given the four days notice required of the election, and the election was voided in 1785, although he did not stand there again.[2] Without his knowledge, he was put in as a Whig candidate at Canterbury at the 1790 election, but finished at the bottom of the poll.[3] Watson was appointed a deputy lieutenantofNorthamptonshire in April 1793,[4] and of Kent on 29 June.[5]
On 30 November 1785, he married Mary Elizabeth Milles (1767–1818), only daughter and heiress of Richard Milles (c. 1735 – 1820),[13]aMember of Parliament for Canterbury from 1761 to 1780.[14] They had seven children:
