He was Captain in the 54th (Highland) Regiment of Foot. M.P. (Tory) for Perth 1761-1764. Due to his own father's attainder, his right of succession was doubtful and on his uncle's death he presented a petition to the Crown. On 7 February 1764, the House of Lords resolved "that the Petitioner hath a right to the titles, honours and dignities of Duke of Atholl, Marquess of Tullibardine, Earl of Strathtay and Strathardle, Viscount Balquhidar, Glenalmond and Glenlyon, Lord Murray, Balvenie and Gask". He was chosen a Representative Peer, 21 August 1767, and again in 1768. Knight of The Thistle, 23 December 1767. Grand Master of Freemasons, 1773 till his death.

In 1753 he had married the daughter of his uncle and predecessor. Through inheritance they were sovereigns of the Isle of Man; however, in 1765 they sold these rights for 70,000 Pounds Stirling to the government, retaining the right to present the kings and queens of England with two falcons on the day of coronation as well as manorial, patronage and mineral rights.

He died in a fit of delirium. He was seized with an apoplectic fit, then swallowed a teacupful of hartshorn (something like ammonia), after which he bled violently at the nose and mouth and complained of being so hot that the only cure would be to sit up to his chin in the River Tay. In fact, his reason had gone. At eight o'clock one evening he managed to slip out of the house unseen and, first leaving his hat on the bank of the river, plunged in. His body was found eight miles
downstream the next day.

Source: Leo van de Pas