Running time: 109 minutes.

MICHAEL Apted's Amazing Grace gets its title from to the much loved hymn written by John Newton, for many years captain of an 18th-century slave ship, who underwent a religious conversion, became an evangelical pastor and assuaged his guilt by caring for the poor.

Although the movie gives a powerful account of the campaign by William Wilberforce that eventually succeeded in banning the slave trade, it is not what you might expect. Apted is more interested in the political forces Wilberforce mobilised behind the abolitionist cause than the religious ideas that inspired him, although he does emerge as a genuinely spiritual man who practised what he preached, opening his stately home to the poor and needy and refusing ever to part with any of his staff.

Nor does Amazing Grace bombard us with shocking images of the atrocities inflicted on black slaves on the sugar plantations, since none of this was ever seen by Wilberforce. He leaves such horror to the imagination, putting us instead in the position of an initially sceptical and resentful public Wilberforce seeks to persuade. This is no easy task given that the wealth of the British Empire depended on shipping goods to Africa to trade for slaves, then transporting the slaves across the Atlantic to the West Indies, and finally returning home with sugar, rum and spices.

Despite the backing of England's youngest Prime Minister William Pitt, Wilberforce . . .

who was only 21 when he took his seat in parliament . . . soon ran foul of the all-powerful slave lobby, headed by a wonderfully slimy Ciaran Hinds, who accused him of giving comfort to England's enemies. He might have given up had it not been for the impassioned urging of his young activist wife (Romola Garai). The political machinations, particularly the devious intervention of Charles Fox . . . Michael Gambon at his roguish best . . . are deftly choreographed and not without contemporary resonances.

"You may choose to look the other way but you can never again say you did not know, " says Wilberforce, a warning today's Westminster might well heed.