Four years in the making, the film has been described as “Gravity meets Touching the Void – 100 metres underwater” and tells the story of a commercial diver, Chris Lemons, who is stranded on the seabed with five minutes of oxygen left – but no chance of rescue for more than half an hour.

Following the screening, Plimsoll Productions head of specialist factual Kate Beetham delved into the production process and creative collaboration behind the film with Bristol-based talent Alex Parkinson, who combined the roles of director, producer, writer and director of photography, producer/director Richard da Costa and editor Sam Rogers.

Da Costa had met Lemons when he was working for the oil and gas industry. “Chris was a compelling character and I was gobsmacked to hear his story, so we made an industry film about the incident,” he recalled. A chance meeting with Parkinson led to the pair developing it into a feature documentary.

On getting consent and cooperation from those involved, da Costa said: “It boils down to two things: trust and intention. What I think made getting the divers on board a natural process was, firstly, that we had an existing relationship. Secondly, they understood that our intention was to be authentic in our portrayal of their world and their story.

“We were genuinely interested in telling the story in as accurate a way as we could and we wanted to bring this strange and unknown world to a wider audience. Divers in a saturation chamber are like a family and it is a fascinating dynamic, but we were also very lucky with the characters.”

Alex Parkinson reflected: “I think the authenticity behind it is so important and hopefully so strong throughout the film. Our overall ambition for the film is that the audience won’t just watch it, but experience it too ­– feeling at least some of the tension, fear and emotion the people there on the night did as this incredible story unfolded. We want it to be very immersive.”

On the storytelling techniques used in the film, he added: “Structurally, all the characters in the film own each part of their story, they are brought in when they are needed.”

Sam Rogers discussed the challenge of bringing together the different elements of the story in the edit – reconstruction, archive and interviews – to focus on the power of the narrative and keep the audience on the edge of their seats.

Last Breath was broadcast on BBC Four in May and is now available on Netflix.