THE story of Nottingham social worker Margaret Humphreys' heroic struggle to discover the truth about the 130,000 British children forcibly deported to Australia and, perhaps even more importantly, do something to help the survivors, is a shocking and important one.

It is respectfully and sensitively treated by Jim Loach's film, based on Margaret's memoir Empty Cradles.

Shot largely in Nottingham, with major sections filmed in Australia, the film stars Emily Watson as Humphreys, in a remarkably restrained, assured and skilful performance which was praised by Humphreys herself at the film's Broadway screening.

Whether taking a baby into care as a young mother tearfully begs her not to in the film's grimly ironic opening scene, calmly dealing with the emotive currents of her own family life or confronting the various sceptical, intimidating or just uncaring adversaries ranged against her, Watson is always convincing and never less than commanding.

As two of the UK-born migrants, Hugo Weaving and David Wenham are also effortlessly great. And it's great to see Agent Smith out of The Matrix being driven down some very recognisable Nottingham streets, just as it is to see Watson having a pint in Carrington's Gladstone pub.

The various stories of the migrants are haunting and unforgettable. Many of the children – often told, untruthfully, that their parents were dead – spent years working as little more than slaves and there were numerous cases of physical and sexual abuse. Back home, it was not unusual for parents to be told their kids had been adopted. Amazingly, the scandal did not end until 1970.

Sometimes writer Rona Munro's dialogue seems a little obvious and literal and some of Loach's directorial flourishes don't do much to drive the story. But the film avoids melodrama and tells of things few in the audience will ever be able to forget.