Nelly & Nadine

Magnus Gertten's documentary begins in a similar fashion to the recent Three Minutes: A Lengthening, with a piece of archive film, this time from immediately after the war, as concentration camp survivors arrive in Malmo, Sweden. It's footage with which the director has become intimately familiar with since he first encountered it in 2007, and which was also the jumping off point for his 2011 film Harbour of Hope and 2015's Every Face Has A Name, in which he tried to uncover the histories for some of the survivors shown here. In a way, each film has triggered another, since it was after Sylvie Bianchi - who will become a key figure in this documentary - saw the latter that she came forward with the information that Gertten expands on here.

The person she had recognised was Nadine Hwang, who unlike many of those on the film who smile and wave at the camera, seems more lost in thought. It is the story of this daughter of a Chinese ambassador to Spain that will unfold through the course of this thoughtful and measured film that tells of the love story that blossomed between her and Bianchi's grandmother, Belgian-born opera singer Nelly Mousset-Vos, while the pair were being held at Ravensbrück concentration camp.

It's fair to say that Gertten has hit the jackpot with Bianchi's family archive, which not only contains a wealth of photographs but also a detailed diary kept by Nelly during the war and Super-8 home video that was shot subsequently. Remarkably, despite being split up during the war years, the pair were reunited in the late Forties and went on to live out their lives together in Venezuela.

We learn about the couple's deep love for one another almost at the same time as Bianchi, who has felt so emotional about the whole affair that she has struggled to bring herself to tackle the archive. Her discovery and the processing of her own emotions acts as a sort of Who Do You Think You Are? counterpoint to the first-person accounts we hear from Nelly and the footage and photographs of them after the war.

The love story is remarkable in its own right but the film also shows the way these sorts of histories could be hidden in plain sight. Bianchi hadn't thought of her grandma as being part of a romantic couple with Nadine as a child, but rather just a friend who she lived with, and though it has obviously become more evident to her as she has grown older, there's a real growing understanding at work of her gran's history, and Bianchi's mum's struggles with that that is evident during the course of the film. Gertten takes his time, using the pastoral setting of Bianchi's farm to add a contemplative element, while some of Nelly's recordings a poignancy to the soundtrack.

This film is a gift that keeps on giving, not just in terms of a historical lesson that can be learned by anyone who cares to take the time to watch it, but also in the concrete way experiences here are shown to directly inspire someone else Bianchi meets during the course of her investigations to live their own truth.