If you're trying to make a somewhat heavy story about the abolition of slavery palatable to the majority of the cinema-going public, picking Welsh Actor Ioan Gruffudd ('Black Hawk Down', 'Fantastic Four') to play the lead role of William Wilberforce was a good move. Gruffudd is able to convincingly portray his character's passionate struggle against injustice over a period of 20 years - as well as being attractive to watch while he does it. Also, and very importantly for what could have turned into an interminable historical epic, 'Amazing Grace' has a well-paced script from the pen of Steven Knight ('Dirty Pretty Things').

Opening with Wilberforce arriving at his cousin's home in 1797, seriously ill and broken from 10 years of work in parliament, much of the first part of the film is by way of flashback. While courting his wife-to-be, the opinionated Barbara Spooner (Garai), Wilberforce recalls his work in the abolition campaign, the hardships and small victories, the friendships and relationships that inspired him.

One of the most important of these is reformed slave trader John Newton (Finney), an evangelical Anglican clergyman and the composer of the classic hymn, 'Amazing Grace'. He was also strongly influenced by Thomas Clarkson (Sewell), a tireless and intemperate advocate of the anti-slavery movement, and Olaudah Equiano (N'Dour) an articulate freed slave whose gentle manner and book about his own experience was a persuasive argument against slavery. Urged by Barbara to take up the cause once again, Wilberforce sets his shoulder to the wheel. In 1807, after 20 long years of struggle, the film ends with the bill finally being carried.

'Amazing Grace' comes bowed down under the weight of historical significance but it is to the credit of all involved that it continually strikes the right note and doesn't get too bogged down in what was a terribly long and difficult political battle. The House of Commons debates, peopled with opponents Lord Tarleton (Hinds), the affected Duke of Clarence (Jones) and friends - Prime Minister-in-waiting William Pitt (an intriguing Cumberbatch) and the realistic Lord Charles Fox (Gambon) - are alive with passion, wit and political intrigue.

The film features a great selection of British thespian heavyweights, all acting their socks off. Their characters are richly developed - whole movies could be made about any one of N'Dour's, Cumberbatch's and Sewell's characters - but Albert Finney's magnificent portrayal of John Newton stands out from the rest. 'Amazing Grace' is worth going to for the acting but staying at for the message: one man, with his heart in the right political position, can make an enormous difference.

Caroline Hennessy