During the last months of Wishart's life Knox was his constant attendant.

His own preaching continued the work of the martyr until June, 1547, when St.Andrews was captured by the French fleet and Knox was made a galley slave for nineteen months.

Under the lash and, what grieved him even more, constantly plied with suggestions that he should "commit idolatry" in praying to the image of Mary, his heart grew bitter against the French and their religion.
Released, either through the influence of the English government, [Sidenote: January 1549] or by an exchange of prisoners, Knox spent the next five years in England.

After filling positions as preacher at Berwick and Newcastle, [Sidenote: 1551] he was appointed royal chaplain and was offered the bishopric of Rochester, which he declined because he foresaw the troubles under Mary.

As the pioneer of Puritanism in England he used his influence to make the Book of Common Prayer more Protestant.