He remained a close prisoner in England till his release after the battle of Bannockburn in 1314. He was then quite blind, and survived his captivity only for two years. Though it is impossible to reconcile his frequent changes, his repeated perjuries and breaches of sworn allegiance to King Edward, with ordinary rules of integrity, yet his unvarying devotion to Bruce has secured him in the affectionate remembrance of his countrymen. His severest critic cannot allege that he ever calculated which side was likely to win. When Balliol renounced his allegiance to Edward, Wishart must have foreseen the hopelessness of resisting the power of England; yet he did resist it, in season and out of season, from the pulpit and from the saddle of his charger. When Bruce came to him, a solitary fugitive from justice, the warm-hearted prelate gave him absolution, and hastened to prepare for his coronation. In his eyes, all means were justifiable to secure the independence of his country. He even used the timber which King Edward gave for a new belfry to Glasgow Cathedral to make engines of war against the castles held by the English.
His deep love for the Bruce was fully returned, and King Robert gave passing expression to it in a charter of lands granted to the bishopric during Wishart's captivity, dated April 26, 1309.
"We feel in the depth of our heart the imprisonment and chains, the persecution and duress, which the venerable father, Lord Robert, by the grace of God Bishop of Glasgow, has hitherto endured and still patiently endures, for the rights of the Church and our kingdom of Scotland."