[1] In 1649 Swinton was returned to parliament for The Merse, and in that capacity opposed the despatch of a deputation to Breda to treat with Charles II.
[3] In consequence of his defection, on 30 January 1651 he was sentenced of death and forfeiture was pronounced against him by the Scottish parliament at Perth, and he was excommunicated by the Kirk.
[4] Swinton was present at the Battle of Worcester on 3 September 1651, but took no part in the conflict, in which two of his brothers were engaged on the Scottish side, and in which Robert, the younger, lost his life in an attempt to capture Cromwell's standard.
[4] Cromwell's victory at Worcester gave Swinton complete control of the Scottish government, and he proceeded to remodel the administration.
On 4 November 1656, by order of council, the sentence of forfeiture pronounced on him by the Scottish parliament was revoked,[7] and he was further recompensed by a part of the Earl of Lauderdale's forfeited estates (see Cromwell's Act of Grace).
On 20 July 1660 he was arrested in London in the house of a Quaker in King Street, Westminster, sent to Leith in the frigate HMS Eagle together with the Marquess of Argyll, and confined in the Tolbooth at Edinburgh.
[4][8] He married, first, in 1645, Margaret, daughter of William Stewart, 2nd Lord Blantyre, and first cousin of Frances Teresa Stuart, duchess of Richmond and Lennox.