Douglas belonged to a junior branch of the Queensberry family, on whose interest he contested Dumfries Burghs unsuccessfully at a by-election in 1735. Returned as a Tory for the county in 1741, he voted against the Government. He was related to Lord Traquair, the chief intermediary between the English and Scottish Jacobites in the negotiations leading to the Forty-five, in which his brothers were involved.1A List of Persons concerned in the Rebellion 1745-6 (Sc. Hist. Soc. viii), 143. In January 1746, during the siege of the castle of Stirling, he arrived from London to see the Young Pretender, with reports of messages sent to France by the English Jacobite leaders, Lord Barrymore and Sir Watkin Williams Wynn, and with the news that the sum of £10,000 was lying in the city of London for the Prince’s use.2Murray of Broughton, Memorials (Sc. Hist. Soc. xxvii), 433-4, 437-8. This was disclosed by Murray of Broughton, the Young Pretender’s secretary, who turned King’s evidence, with the result that in August 1746 Douglas was sent to the Tower, the House being notified of his arrest for high treason.3CJ, xxv. 184. At a meeting of the Privy Council, 11 Nov.,
Sir John Douglas being then asked what he has to say to the facts above mentioned [Murray’s evidence] he saith that he shall make no answer in any shape, that perhaps this may be ill manners, but that being no lawyer he doth not think fit to give any answer.4Murray of Broughton, 452.
Attempts to get corroborative evidence5Ibid. 462-3; The Lyon in Mourning (Sc. Hist. Soc. xxi), ii. 238. having failed, he was released in March 1748 on bail of £4,000.6Gent. Mag. 1748, p. 138. Excepted by name from the subsequent Act of Indemnity, 20 Geo. II, c.52, he did not stand again. He died 13 Nov. 1778.