Thomas Hay, Lord Kinnoull, formerly Lord Dupplin, who wrote to the Duke of Atholl on the conclusion of the Revestment.

His letter is dated from Dupplin on 9 March 1765. Mr Mackenzie had already told him of what he called the happy conclusion of the Duke's troublesome and interesting business, and he wrote to congratulate the Duke and Duchess. He could form no judgement, he said, how far the compensation was adequate to the loss the Duke would suffer in his income, but it was his clear opinion that all circumstances considered the agreement was one it had been proper, wise and prudent to accede to, for the benefit of the family as well as for the Duke's own ease and security. He put the success in an arduous and delicate transaction down to the Duke's firmness, moderation and spirit, and thought the hard and severe trials he had undergone since coming into his honours and estate had gained him credit as well as experience. In the same letter he reported that no performance at the Bar of the House of Commons had been spoken of with such universal and high applause as Mr Cooper's since Lord Mansfield left that Bar.

He was a Treasury politician of the Newcastle connection. He succeeded his father in July 1758 and had been on an embassy to Portugal. Newcastle thought him indispensable and told him in September 1760 that he could do nothing well in a new Parliament without him, though the world at large, as Namier records, held him opprobriously and injuriously to be an absolute fool. He resigned the Chancellorship of the Duchy in anger when the Duke of Devonshire's name was struck out of the Privy Council in November 1762, and when Newcastle went into opposition he withdrew from politics altogether.