The most influential person of the Scottish Reformation, John Knox, was first ordained as a Catholic priest.
Knox spent time in the company of George Wishart before he was arrested and burned for heresy in March 1546 by Cardinal Beaton. Knox joined the Reformers, who murdered Cardinal Beaton the following May.
He continued on a path of theological study that took him across a changing Europe and ever further from the weakening Vatican. St Giles Cathedral in Edinburgh was where, in 1559, John Knox was ordained as a minister, and his sermons there helped push Catholicism out of Scotland.