Oscar, Golden Globe and BAFTA winner Sam Mendes is directing his first documentary, What They Found, for BBC Two and iPlayer, which uses archive footage and first-hand testimonies to tell the story of two members of the British Army’s Film and Photographic Unit who accompanied the troops liberating Bergen-Belsen at the end of the Second World War.

The film, which is due to air in April to mark the 80th anniversary of the liberation, is being produced by Lightbox in association with Sam Mendes and Pippa Harris’s Neal Street Productions, and Imperial War Museums.

On 15 April 1945, British soldier-cameramen Sgt. Mike Lewis and Sgt. Bill Lawrie, members of the Army Film and Photographic Unit covering the campaign in North West Europe, accompanied British troops to what they were told was a typhus hospital in Northern Germany, named Bergen-Belsen. When they arrived there, the full horrors of what was going on inside the camp were revealed to them and, through their footage, to the world – for the first time.

What They Found immerses audiences in Lewis and Lawrie’s footage and words, to create an intimate and deeply personal record of two ordinary men’s experience of the war and, through them, of the trauma and tragedy of the Holocaust.

Sam Mendes said: “Using only the voices and footage shot by two British army cameramen during the latter stages of the Second World War, I hope this documentary gives a unique perspective on the discovery of the horrors of Belsen, and the reality of the Holocaust.”

Simon Young, Head of Commissioning, History, said: “In April 1945, BBC Radio broadcast a horrifying eyewitness report from Bergen-Belsen. There could be no more fitting way to mark the anniversary of the liberation than by working with Sam Mendes and his team to create a chilling vision of what the liberators found. It has been an honour to collaborate with the Imperial War Museum, Lightbox and Neal Street on this unique project.”

Simon Chinn and Jonathan Chinn, Producers of What They Found, and co-Founders of Lightbox added: “The last survivors and witnesses to the Nazi atrocities at Bergen-Belsen and elsewhere sadly won’t be with us for much longer. Through making What They Found, Sam Mendes has created a powerful and undeniable record of these events at a time when surveys show that more and more young people aren’t aware of the Holocaust, and its veracity is being debated or denied in ever-increasing numbers.”

The mute, black and white footage shot by Lewis and Lawrie, together with all the unique footage shot by the AFPU, was deposited with the Imperial War Museum by the British War Office in the 1950s. In the 1980s Imperial War Museums (IWM) undertook a series of oral history interviews with Second World War cameramen (conducted by IWM’s former Senior Film Curator Kay Gladstone), including the extraordinary audio testimonies with Lewis and Lawrie.

Dr James Bulgin, Imperial War Museums’ Head of Public History and curatorial expert on the Holocaust said: “The sights captured by the AFPU cameramen who were present at the liberation of Bergen-Belsen have left an indelible mark on the world. What They Found uses IWM’s collections to give those scenes critical context, describing them from the unique perspective of those who witnessed them first hand. The film is a searing and timely reminder that each person caught up in this terrible history experienced it as an individual.”

What They Found is directed by Sam Mendes and is a Lightbox production in association with Neal Street and Imperial War Museums. Producers are Simon Chinn, Jonathan Chinn and Gaby Aung. Executive Producers are Pippa Harris for Neal Street, Caro Howell and Vicky Stanbury for Imperial War Museums and David Baddiel. Vanessa Tovell serves as co-producer for Lightbox and the editor is Andy Worboys. The film was commissioned by Jack Bootle, Head of Commissioning, Specialist Factual. The Commission Editor is Simon Young, Head of Commissioning, History for the BBC, and All3Media International is the worldwide distribution partner.