Sometimes the ambition of a Doctor Who story utterly outstrips the production’s ability to deliver and 1977’s ‘The Invisible Enemy’ is a case in point.

The story, involving a sentient space virus which infects the Doctor and prompts a Fantastic Voyage style adventure into the Time Lord’s head, is probably best remembered for the introduction of the Doctor’s robot dog companion K-9 or for the excellent catchphrase “Contact has been made”. Less so for the realisation of the virus itself, which is lovingly rendered as a sort of giant space prawn.

However, as with many of the Doctor’s less visually impressive adventures, any fault lay in the execution and its strong ideas are what writer Jonathan Morris has played with and extrapolated to create ‘Revenge of the Swarm’, set free by the limitless set budgets of the medium.

Picking up with the crew of the Seventh Doctor, Ace and Hector, a vestige of the swarm which once infected the TARDIS computer core exploits a vulnerability in the latter’s damaged brain (the consequence of a previous adventure which has wiped him of his original personality and memories). Overwhelming him, it pilots the TARDIS to the moon of Titan, one of the scenes of the original adventure.

What follows is a clever tale which serves as both prequel and sequel as the virus not only brings about its own genesis, but employs the cloning technique of geneticist Dr Kilbracken to ensure its continued survival two hundred years into the future.

As well as examining the creation of the swarm, which the Doctor seems happy to accept as a fait accompli, we are also granted an insight into its motivation and grand desires too.

Although he is most famous for K-9, John Leeson also voiced the Nucleus in the original tale and returns to that role here, losing none of its pomposity or penchant for self-aggrandising. As the story progresses, he gets to develop the voice as the power of the swarm grows.

The supporting cast include Phyllida Nash as Kilbraken, who plays a superbly superior sort of scientist with some dubious ethics, and Siobhan Redman who has been since cast as Big Finish’s new incarnation of The Rani.

Mirroring our obsession with online connectivity, humanity has spread to the stars but remained connected via the Hypernet and there are some spot on gags, with text messaging also receiving an amusing little dig which picks up on the phonetic spelling of the year 5000.

Like the original this is fast and fun, not taking itself too seriously and cleverly providing a false ending before spinning off into the future section for the second half of the tale. In amongst all that fun though, there is a darker message as the Doctor’s actions provide Hector (nee Hex) with a shocking insight into how far the Time Lord is prepared to go to save the day.

Extras: Approximately fifteen minutes of interviews with the cast and crew, including John Leeson discussing his surprise at returning to the role of the Nucleus after so long.

Released in September 2014 by Big Finish Productions Ltd.

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