As our film was to be a forensic, minute-by-minute account, we decided to focus on just two elements: the testimonies of witnesses, and archive material shot on the day.

That put an emphasis on the interviews, and I worked with cameraman Ross Keith to give a particular intensity to the look of those first-hand accounts. We hunted out locations that would allow us to set up the camera at an unintimidating distance from the interviewees. I put the questions sitting closer to the witnesses, just outside the frame, allowing Ross to shoot on a long lens that would diffuse the backgrounds to concentrate intently on faces.

We chose not to employ reconstruction, CGI or graphics, preferring the authenticity of archive material gathered on the day. We tracked down every frame we could find, including reports from local TV stations, and an extraordinary range of photographs recording the sequence of events.

The archive was crucial in providing the immersive sense of the day we were aiming to create. Amateur homemovie footage was a particularly rich source.

We were always on the lookout for archive that related directly to the stories of our witnesses. There was a special frisson when we were able to illustrate the Newman family’s account of diving to the ground to shield their kids as the shots rang out in Dealey Plaza with archive that captured them at that exact moment.

We also made our own discoveries. James Tague told us how he became the only bystander to be wounded in Dealey Plaza, grazed by a ricochet from one of the assassin’s shots. In a photograph of the chaos after the shooting, we found a shadowy image of Tague at that instant. It had been unnoticed in the archive for 50 years.