These questions lie at the heart of Oranges and Sunshine, the based-on-a-true-story directorial debut from Jim Loach.

In February last year Gordon Brown attempted to explain why tens of thousands of British children were plucked from an over-wrought welfare system, told their mothers and fathers were dead and shipped off to work in the Australian colonies, often ending up as the victims of institutional abuse. Brown offered to help these displaced orphans trace their lost families. Then, on behalf of the country, he apologised unreservedly.

His actions were largely due to the campaign of social worker Margaret Humphreys, played here with characteristic discretion by the lovely Emily Watson. Humphreys, with the initial backing of the local authorities, spent 23 years listening to the stories of child migrants before searching for their lost parents, and has been gifted a CBE and a biopic for her efforts.

As Loach’s film shows, some of these people have to learn how to live with fathers who walked out, with women who bore them but could not raise them. For others, they had stone graves and hazy anecdotes waiting for comfort; their reunion came too late.

At its worst, we see slow montages of older Australian men, stuttering and choking as they recall the years of abuse they suffered at the isolated orphanage in which they were raised. This abuse was physical and sexual and to exhume it places the film on precarious ground. Pity can go too far, and misery is cheap and easy; a perishable commodity.

But Loach, in his father’s best tradition, manages to steer the film to the fault-lines of broken restraint, showing wounds that open and close just as quickly. These moments reach out from the screen, particularly through performances from Hugo Weaving and David Wenham.

Oranges and Sunshine  is softly rendered, and not exactly interrogative. Margaret Humphreys is held aloft in her simple goodness (“I don’t ever lie,” she says to a heckling woman), and as the film rushes to its climax, it begins to veer from knock-out scene to knock-out scene, unraveling some of the sensitivities and carefully posed questions of its earlier acts.

But no matter. This is a film of brevity, depth and regard; desperately sad, but as clear and honest as a voice across water. Ken, the boy’s done good.