This historical personage was fourth son of Sir Oliver St.Clair of Roslin, the favourite son of William St.Clair, Earl of Orkney and Caithness, last Lord of the Isles. His name figures frequently in Orcadian, Scottish, and English national records. A staunch Romanist, he was a favourite with James the Fifth, over whom he had a great influence. For these reasons he and his brothers incurred the special displeasure of the reformer Knox, who tells us that "many of King James' minzeons were pensioners to priests; amongst whom, Oliver Synclare, yet remaining enemy to God, was the principal". He was Governor of Tantallon Castle in 1540, when Sadler, the English ambassador, narrowly escaped seizure by him; and on 20th April 1541, on rescission of Lady Sinclair's grant of Orkney, the Isles were committed to him as Donatary [a grantee of the Crown Skatts, Males, and Duties] of the Tack [Lease].
The most eventful incident with which the Minion is associated is the Scottish surrender at Solway Moss on the 23rd November 1542. The account of this so-called battle has usually been related to his disparagement, and it is fitting that his memory should now be vindicated, although it may be a tardy removal of an unfair verdict. It had long been the wish of the Scottish Catholics to involve James V in war with his English uncle. Assembling an army, he advanced to Berwick and wished to enter England, but the nobility refused to follow him, Mortified by their action, he resolved to re-muster forces for an expedition to be known as his own raid. On approaching the river Esk the halt was sounded, and Oliver Sinclair was elevated on the "shield of war" to read the royal commission proclaiming him commander-in-chief. The disloyally affected nobles seized the appointment as a pretext for again thwarting their sovereign, and allowed themselves to he captured by a small party of English cavalry. The effect on King James was electrical; crushed in spirit, he died within a few days after the event. The captured nobles on their return formed a political faction with English interests, known as the "Assured Lords".
On the restoration of the Earl of Arran's government in 1584 Oliver Sinclair of "Solway Moss" made his historical exit in an object lesson to that bastard upstart. One day when the favourite was hustling into the Court of Justice, at the head of his numerous retinue, an old man, indifferently dressed; chanced to stand in his way. As Arran pushed rudely past him, the old man, stopping him, said, "Look at me, my lord, - I am Oliver Sinclair". Oliver, as favourite of James V, had exercised during his reign as absolute a sway in Scotland as Arran now enjoyed under his grandson James VI In presenting himself before the present favourite in his neglected condition, he gave Arran an example of the changeful character of court favour. The lesson was a striking one, but Arran did not profit by it.