[9] Richmond was appointed British ambassador extraordinary in Paris and made a Privy Counsellor in 1765, and in the following year he briefly served as Southern Secretary in the Rockingham Whig administration, resigning office on the accession of Pitt the Elder in July 1766.

[2] He was promoted to lieutenant general on 30 April 1770[10] and was briefly leader of the parliamentary Whigs in opposition in 1771 when Rockingham's wife was ill.[2] Richmond's anti-colonial positions earned him the epithet "the radical duke.

[2] Nevertheless, as Lord Lieutenant he raised the Sussex Militia for home defence and took personal command as Colonel (a position he held until 1804, despite his advanced age).

[14] In 1779 Richmond brought forward a motion for retrenchment of the civil list, and in 1780 he embodied in a bill his proposals for parliamentary reform, which included manhood suffrage, annual parliaments and equal electoral areas.

[16] Richmond joined the Second Rockingham Ministry as Master-General of the Ordnance in March 1782;[15] he was appointed a Knight of the Garter on 17 April 1782[17] and promoted to full general on 20 November 1782.

[2][15] In November 1795, when Thomas Hardy and John Horne Tooke were charged with treason and cited his publications on reform in their defence, Richmond became a liability to the Government and was dismissed in February 1795.

[10] On April 21, 2017, the Declaration Resources Project at Harvard University announced that a second parchment manuscript copy had been discovered at West Sussex Record Office in Chichester, England.

How it came to be in England is not yet known, but the finders believe that the randomness of the signatures points to an origin with signatory James Wilson, who had argued strongly that the Declaration was made not by the States but by the whole people.