The Asphyx

• Director Peter Newbrook spent most of his career as a cinematographer and camera operator (he worked under Freddie Young on David Lean epics) and as a producer — The Asphyx was his one and only directing credit.
• The Cunningham manor exteriors were shot at Foxhills, near Ottershaw/Chertsey in Surrey (also used in The Oblong Box), with studio work done at Shepperton Studios; the film's modern-day epilogue car-crash scene was filmed at the Winstanley Estate in Battersea, London.
• Lead actor Robert Stephens had been one of the leading men of Britain's National Theatre in the Olivier era and was once tipped as Olivier's natural successor, but by the time of The Asphyx (1972) his career was sliding amid heavy drinking, coinciding with his 1970 exit from the National Theatre and the collapse of his marriage in 1973 — his acclaimed Royal Shakespeare Company run (Falstaff, Julius Caesar, King Lear) didn't come until the early 1990s.
• The screenplay was written by Brian Comport, based on an original story idea credited to Christina and Laurence Beers.
• Contemporary critics were unkind — the Monthly Film Bulletin dismissed it as a static, cliche-ridden vanity piece for Stephens — and the film flopped on release, but it built a cult following over the decades: it made Martin Scorsese's list of 50 favorite British films, which he sent to director Edgar Wright during COVID lockdown, with Wright singling it out as a movie he'd assumed only he and his brother had ever seen.
• The film was also released under the alternate titles Spirit of the Dead and The Horror of Death.

The Asphyx is not a supernatural entity but a projection of Hugo's own psyche — his obsession with death has externalized his guilt into a visible form. Every captured Asphyx is a fragment of his soul he's been photographing away.

The film is a covert critique of scientific positivism and the Victorian gentleman-scientist as a moral failure. Hugo's inability to distinguish between knowledge and wisdom makes him worse than the superstitions he dismisses.

Immortality in the film is not life extended but death deferred — the Asphyx's victims are trapped in the moment of dying forever, making the 'gift' of eternal life indistinguishable from eternal suffering.

Victorian scientist Sir Hugo Cunningham belongs to a parapsychological society that photographs people at the moment of death, believing the ghostly blur that shows up on film is the departing soul. After a boating accident kills his son and future daughter-in-law, Hugo studies his own home-movie footage and realizes the blur isn't leaving the dying — it's coming for them. He names it the "Asphyx," a personal spirit of death out of Greek myth. Experimenting further, he finds that an intense light made from phosphorus and water can freeze an Asphyx in place at the instant of near-death, trapping it and making its target immortal. Hugo tests the process on himself with a rigged electric chair, then pulls his ward Christina and adopted son Giles into a guillotine experiment meant to make them immortal too — until a malfunction turns the trial fatal. The film's real argument: trapping death's spirit to cheat it is just a slower, crueler way of dying.