There is no doubt that Christina Noble, the subject of this biopic from writer/ director Stephen Bradley, should be better known. The Irish campaigner and fundraiser has done an enormous amount for dispossessed children in Vietnam and Mongolia – setting up a foundation which runs over 100 projects in those countries which have improved the lives of nearly a quarter of a million children and their families. The film has the very laudable aim of explaining how her life has led her down that particular path, and all the travails she has overcome to do so.

The film contrasts Christina’s first visit to Vietnam, seeing the deprived street children in 1989, with her own poor upbringing in Ireland in the 1950s. It is a well worn, but useful shorthand for the filmmaker – the duality of story, and we are clearly shown that comparisons should definitely be drawn. Combined with her experience of homelessness as a young woman, we clearly understand her response to the deprivation these children are going through is with more than the usual level of empathetic concern. We’ve seen that moment of her past, we can see why she responds with such heartbreak to the homeless children around her.

But what’s more intriguing is that the thing which drove her to Vietnam just fourteen years after the end of the war – a dream about the country she’d had as her marriage was ending twenty years before. And alas, this – the gap between the dream and finally reaching Vietnam – is where the film falls slightly short.

Noble’s childhood as the poor bolshy kid who just wants to sing, and then as the young woman who’s just trying to get on in life despite huge amounts of trauma and tragedy, is well covered. But the moment which leads her to focus the rest of her life on the pursuit of Vietnam happens in a dream and is left hanging. We see her at all ages talking angrily to God in otherwise silent churches, and never really being given the answers that she seeks – yet when the dream of Vietnam comes, no real explanation or exploration is made of why it has happened – the story picks up many years later with her arrival in the country, after a period of her life we learn very little about. It would have been nice to have visited her during that undocumented time to see why a country she once dreamed about was still driving her actions.

The core performances are excellent. Deidre O’Kane as the adult Christina Noble is the heart of the film, with a real persuasive and spiky charm which makes you understand how a lone figure visiting a country she had never been to before could make such a huge change. Sarah Greene as her younger self is also excellent – a wounded but unbeaten quality which drives the explanatory narrative and links the the two stages of her life with skill. Ruth Negga as her friend Joan in the 1950s and 60s is as reliably brilliant as ever, turning in a wonderfully magnetic performance which brings her character absolutely to life during the limited number of times she appears on screen. Nhu Quyhn Nguyen as Madame Linh, the manager of the orphanage Noble is trying to help, additionally heads a cast of Vietnamese actors doing good supportive work. Liam Cunningham, as Christina’s alcoholic father Thomas, is also great – a brooding, broken man, coated in shame.

Stephen Bradley directs his own script with a deft hand. Humour and music is used to good effect. The sequences in 1950s Ireland, and 1960s Birmingham are done with an eye for detail which is impressive, and the scenes of 1980s Vietnam filmed in Ho Chi Minh City give a real sense of a country undergoing change, coaxing excellent performances. There are moments throughout the film, in all time periods, which disturb with their quietly stoic horror.

It’s just a shame that in telling a life story of how a vision drove somebody to do something, that the moment after that initial dream is not followed up upon. We discover little of what happened between Noble leaving for London as a young mother and arriving in Vietnam many years later as an adult woman; a whole section of her life during which the idea of Vietnam must have driven her forward, is mostly missing.

And as such, that important driving desire, that energy, is missing from the film. It would have been nice to see.

When we meet the real Christina Noble during the closing titles, in the way that biopics inevitably end, as well as being impressed by her indefatigable nature, we also find ourselves wanting to know more.

Noble is out in UK cinemas on Friday 12th November.