He succeeded to the family estates on his father's death on 10 September 1654, but after escaping to the continent, remained in exile until the Restoration, occupying much of his leisure in the study of law.

[1] In their policy on behalf of episcopacy, Middleton and Tarbat found themselves at this time opposed by John Maitland, 1st Duke of Lauderdale, the Minister for Scottish Affairs.

They resolved therefore, to ruin him, the design being that Tarbat, who 'was then much considered at court, as one of the most extraordinary men that Scotland had produced', should succeed to Lauderdale's place as Secretary of State.

Further inquiry, instigated by Lauderdale, led to the discovery that Middleton had been misleading both the king and the parliament, and he was dismissed from office, while Tarbat, for his connection with the intrigue, was on 16 February 1664 deprived of his seat on the bench.

[1] He remained in disgrace till 1678, when, through the offices of Sharp with the Duke and Duchess of Lauderdale, he was on 16 October appointed Lord Justice General of Scotland.

In 1683 he bought an estate north of Edinburgh belonging to Andrew Logan and built Royston House (later renamed Caroline Park), which in 1705 he unsuccessfully tried to sell to the government as an official residence for the Lord Chancellor.

[2] Shortly after the accession of James II, he was on 15 February 1685 created Viscount of Tarbat and Lord Macleod and Castlehaven in the peerage of Scotland to him and heirs male of his body.

In the 'Leven and Melville Papers' (p. 14) there is printed, under date 25 April 1689, an exoneration and discharge to him of his office of register, securing him – on account of his faithful service both in putting 'in order and method' the various documents under his charge and recovering many that were missing — 'from all danger in his person or estate, notwithstanding of any acts, writings, councils, speeches, or any crimes committed by him.'

[1] Lockhart states that though 'he pretended to favour the Royal Family [the family in exile] and the episcopal clergy, yet he never did one act in favour of any of them, excepting that when he was secretary to Queen Anne he procured an Act of Indemnity and a letter from her recommending the episcopal clergy to the Privy Council's protection; but whether this proceeded from a desire and design of serving them is easy to determine when we consider that no sooner did Queen Anne desert the Tory party and maxims, but his Lordship turned as great a Whig as the best of them, joined with Tweedale's party to advance the Hanoverian succession in the Parliament 1704, and was at last a zealous stickler and writer in favour of the Union'.

He was consulted by Sir Robert Moray in regard to the formation of the Royal Society of London, and contributed to its 'Transactions' the following papers: An 'Account of Hirta and Rona' (islands of the Hebrides) was published in 'Miscellanea Scotica,' 1818, ii.