If you're going to abolish the obscenely profitable 18th century slave trade then it would help to have Fantastic Four's Mr Fantastic onside.

Ioan Gruffudd - who played the superhero in the Marvel Comics big screen outing - swaps his blue spandex suit for pantaloons and a blouson for this sober biopic.

He portrays the radical idealist William Wilberforce, the 18th century MP who steered the bill abolishing slavery through an initially hostile Parliament.

It's a compelling yarn as the young Wilberforce gathers a spiky group of fellow thinkers around him to defeat a hardcore of MPs with a vested interest in keeping the slave ships sailing.

Rallying to his liberal flag are radical agitator Thomas Clarkson (Sewell) and Lord Fox (Gambon), who controversially crossed the floor of the house to join the anti-slavery group.

At home, support came in the form of Wilberforce's loyal wife Barbara (Garai), a feisty champion of the abolition movement.

It's the sort of solid film you might imagine on the History Channel, boasting decent performances to shed light on a key player in British political history.

Wilberforce - subtly played by Gruffudd - waxes between the call of evangelical Christianity and the powerful pull of the floor of Parliament as an uncompromised independent MP.

On the downside, the tone is uneven as the chronology confusingly switches back and forth and the dialogue occasionally lumbers into dogma.

However, it's an illuminating, handsomely mounted piece celebrating that rare thing - a political movement that was genuinely a force for good.

By the way, the title is taken from Wilberforce's rendering of the uplifting hymn to demonstrate to the pro-slavery lobby that he meant business.

Tim Evans