Heron’s family had long been active in opposition to the interest of the earls of Galloway in the Stewartry, but had not returned the Member since 1768. Heron himself was defeated in 1774 and his protégés in 1780 and 1784. On a vacancy in 1795, however, he was returned unopposed, after making a pact with Henry Dundas’s support, which was the more readily given for Heron’s services in combating the Scottish reform movement in 1792. The pact involved sharing the seat with Richard Oswald and Dunbar Douglas, each to sit two years. Again with Dundas’s assistance, Heron contrived to retain the seat for himself.
Dundas had deplored Galloway’s opposition to Heron, ‘than whom there is not a more respectable gentleman or friend of government in the House of Commons’.
On the eve of leaving London after the loss of his seat Heron wrote to Addington that
the same sentiments which attached me to you on your coming into administration still operate in my mind as powerfully as ever, from the opinion and belief that your whole conduct has been regulated by that integrity and anxiety for the true interest and welfare of your country which induced you to assume the reins of government.
Sidmouth mss, Heron to Addington, 29 May 1803.
‘Now retiring to the quiet of a domestic life’, he wished Addington ‘every possible success’. He died, aged 67, at Grantham on his way home, 9 June 1803.