How do you make the slavery debates of 18th-century British parliament cinematic? Amazing Grace does so by casting some of the best brogues around. This biopic of abolitionist crusader William Wilberforce (Ioan Gruffudd) gains much of its force from the supporting players, including Albert Finney as John Newton, former slave captain and author of the title hymn, and Michael Gambon as one of Wilberforce’s political allies. These and others turn what could have been a drab, overly earnest historical drama into a gripping insider’s look at British politics. Director Michael Apted also offers a refreshingly nuanced consideration of Wilberforce’s Christianity and how it shaped his politics.