He had early in life, as Lord Lorne, been entrusted with the possession of the Argyll estates when his father renounced Protestantism and took arms for Philip III of Spain; and he exercised over Clan Campbell an authority almost absolute, disposing of a force of 20,000 retainers, being, according to Baillie, "by far the most powerful subject in the kingdom".

[2] Contemporaries said he had a very charming and persuasive manner,[2] although early in life he developed a habit of abruptly leaving the room if a conversation took a turn he did not like.

In 1638, the king summoned him, together with the earls of Traquair and Roxburgh, to London, but he refused to be won over, warned Charles against his despotic ecclesiastical policy, and showed great hostility towards William Laud.

Argyll, who inherited the title at the death of his father in 1638, originally had no preference for Presbyterianism, but now definitely took the side of the Covenanters in defence of national religion and liberties.

[1][4] Argyll continued to attend the meetings of the General Assembly of the Church of Scotland after its dissolution by the Marquess of Hamilton, when Episcopacy was abolished.

After the Pacification of Berwick, he carried a motion, in opposition to James Graham, 1st Marquess of Montrose, by which the estates secured to themselves the election of the lords of the articles, who had formerly been nominated by the king.

This was a fundamental change to the Scottish constitution, whereby the management of public affairs was entrusted to a representative body and withdrawn from the control of the crown.

He transferred control over judicial and political appointments to the parliament, created Argyll a marquess in 1641, and returned home, having, in Clarendon's words, made a perfect deed of gift of that kingdom.

Argyll was mainly instrumental in this crisis in keeping the national party faithful to what was to him evidently the common cause, and in accomplishing the alliance with the Long Parliament in 1643.

In July, he advanced to abet the Irish troops now landed in Argyll, which were fighting in conjunction with Montrose, who had put himself at the head of the Royalist forces in Scotland.

[6] Argyll supported the invitation from the Covenanters to Charles II to land in Scotland, and gazed upon the captured Montrose, bound on a cart to execution at Edinburgh.

After the defeat of Dunbar, Charles retained his support by the promise of a dukedom and the Garter, and an attempt was made by Argyll to marry the king to his daughter, Lady Anne.

He was hopelessly in debt, and on terms of such violent hostility with his eldest son and heir Archibald as to be obliged to demand a garrison in his house for his protection.

[6] At the Restoration, Argyll presented himself at Whitehall, but was at once arrested by order of Charles II and placed in the Tower of London (1660), before being sent to Edinburgh to stand trial for high treason.

He was acquitted of complicity in the death of Charles I, and his escape from the whole charge seemed imminent, but the arrival of a packet of letters written by Argyll to Monck showed conclusively his collaboration with Cromwell's Protectorate of England, particularly in the violent suppression of Glencairn's Royalist rising in 1652.