John Mcleod Campbell was appointed minister in 1825. Nearly the whole of Scotland was Calvinist, so when Campbell started to preach that Christ's death offered salvation to all and not just a select few, he stirred up a lot of controversy.
The area around Rhu was filled with a profoundly irreligious population, yet Campbell's passion and his new teaching stirred them and brought about a revival. 'There was an awakening of religious life there which got its first impulse from the Rhu Kirk. Greenock, Glasgow, Edinburgh thrilled as with the gush of a fresh spring-tide.' (Albury Apostles, 'The story of the body known as the Catholic Apostolic Church', by Rowland A Davenport.)
In 1831 he was deposed by the General Assembly of the Church of Scotland for his heretical teaching. He spent the next two years evangelising the Highlands including Greenock in 1832 where around 6,000 heard him preach and where many were converted.
Campbell then ministered for 26 years in Glasgow.
Campbell had a young assistant for a short time (1827) called Alexander J Scott. Scott was possibly the first person to preach in the UK on the Gifts of the Spirit being for today. In 1828 he went to London to work for Edward Irving for a couple of years. Scott was also thrown out of the Church of Scotland by the General Assembly in 1831 for heresy. Like Campbell, he believed in Salvation being offered to all.
The difficulty I find with this revival is whether the atmosphere of revival was over the area already or whether these new doctrines and the passionate preaching of Campbell, Irving and others brought it about. I suspect it was the former.
Another minister, Robert Story, was also preaching these same doctrines in nearby Rosneath. He defended his friend Campbell when the General Assembly came after him and he was in some danger himself, but the furore died down and he was left alone.