Inferno is the fourth and final serial of the seventh season of the British science fiction television series Doctor Who, which was first broadcast in seven weekly parts on BBC1 from 9 May to 20 June 1970.
The Third Doctor and UNIT are called in to investigate a murder at Project Inferno, an effort to drill through the Earth's crust to harness great energies within the planet's core.
It transpires that the drilling is producing a green ooze that transforms all who touch it into savage humanoid creatures called Primords, who can only be killed via extreme cold.
After quarrelling with Stahlman, the Doctor attempts an experiment on the detached TARDIS console, but a freak accident transports him into a parallel space-time continuum.
When the drill penetrates the Earth's crust it unleashes immense amounts of seismic forces, heat, and poisonous gases, along with more of the ooze, which Stahlman's counterpart, now mutated, uses to transform most of the remaining project staff into more Primords.
The Doctor determines that the unleashed energies of the core will eventually disintegrate the planet and is able to persuade the surviving staff members to help him return to his own universe and prevent a similar catastrophe.
They eventually succeed in restoring power to the TARDIS console despite repeated Primord attacks, but Liz's counterpart is forced to kill the Brigade Leader when he turns on the Doctor, who narrowly escapes as the Project Inferno facility, and Britain itself, is destroyed by a massive volcanic eruption.
Scriptwriter Don Houghton was a personal friend of the Doctor Who script editor, Terrance Dicks: they had worked together for Lew Grade at ATV in the 1960s, on the TV soap opera Crossroads.
Stuntman Derek Ware did not actually perform the stunt in which his character, the mutated RSF Trooper Wyatt, having been shot, falls to his death from the top of one of the chemical tanks, in case he was injured (since he was also needed for the subsequent studio recording).
[6] The exterior shots used in this production were filmed at Kingsnorth Industrial Estate on the Hoo peninsula, Kent which featured as the setting for the Inferno project.
[7] Director Douglas Camfield chose not to commission any new incidental music for the serial, but instead made use of existing library recordings by members of the BBC Radiophonic Workshop.
Christopher Benjamin, who plays Sir Keith Gold, subsequently appeared as Henry Gordon Jago in The Talons of Weng-Chiang (1977),[10] and as Colonel Hugh Curbishley in "The Unicorn and the Wasp" (2008).
Ian Fairbairn (Bromley) had previously appeared as Questa in The Macra Terror (1967) and as Gregory in The Invasion, and would subsequently feature as Doctor Chester in The Seeds of Doom (1976).
In 2009, Mark Braxton of Radio Times awarded the serial five stars out of five and praised the intense atmosphere, with a "good, scary, cautionary" plot.
Due to the complexities of conversion, the original re-conversions back to 625-line PAL left the picture looking a little blurred and faded when the story was released on VHS in the UK in May 1994.