For some time he was captain in a company of Lord Loudoun's regiment of foot, afterwards the 54th. Murray sat as
Member of Parliament for
Perthshire from 1761 to 1764. On 8 January 1764, his uncle and father-in-law, the
2nd Duke of Atholl, died. Murray should have been heir to the dukedom, which was only able to descend through the male line; but he was ineligible since his father had fought in the
Jacobite Rising of 1745 and had consequently been
attainted in the blood. However, on 7 February 1764, the
House of Lords deemed Murray the rightful heir to his uncle's title (notwithstanding the attainder of his father) and he succeeded him as 3rd Duke of Atholl. He was elected a
Scottish representative peer in 1766. His wife, on the death of her father, the second duke, succeeded to the
suzerainty of the
Isle of Man, and to the ancient English
barony of Strange, of Knockyn, Wotton, Mohun, Burnel, Basset, and Lacy. For some time negotiations had been in progress with the British government for the revestment of the suzerainty back to the British crown; and in an act of parliament, the
Isle of Man Purchase Act 1765, was passed to give effect to a contract between the lords of the Treasury and the Duke and Duchess of Atholl for the purchase of the sovereignty of Mann and its dependencies for £70,000, the duke and duchess retaining their manorial rights, the patronage of the bishopric and other ecclesiastical benefices, the fisheries, minerals, etc. The arrangement rendered them very unpopular in Mann, and the
42nd Regiment of Foot, or Black Watch, under Lord John Murray, had to be stationed in the island to maintain order. The money received by the duke and duchess was directed to be laid out and invested in the purchase of lands of inheritance in Scotland, to be inalienably entailed on a certain series of heirs. The duke and duchess had also a grant of an annuity of £2,000 for their lives. Atholl was chosen a Scottish representative peer in succession to the
Earl of Sutherland, who died 21 August 1764, and he was reelected in 1768. In 1767, he was invested with the
Order of the Thistle. The 3rd Duke was patron of the fiddler
Niel Gow and had a hermitage built above the
Black Linn Falls on the River Brann in 1757. He was
Grand Master of the
Ancient Grand Lodge of England from 1771 until 1774, and Grand Master of the Grand Lodge of Scotland from 1773 to 1774. He died at
Dunkeld on 5 November 1774. ==Family==