M is for... Mawdryn

A scientist who, along with a group of colleagues, stole Time Lord technology in order to extend their lifespans. The Metamorphic Symbiosis Generator induced instead a perpetual mutation. Mawdryn's people shunned them and they were exiled in a spaceship. This was programmed to travel from planet to planet, in the hope that one day they might find a cure for their predicament. Every 50 years or so, when the ship came into orbit around a new world, one of the scientists would use a transmat pod to travel down to it to see if the technology existed. The others remained in a state of hibernation on the ship.

Mawdryn was the scientist who used the transmat pod to travel down to Earth in 1977, but the process caused a further mutation which left left him horribly disfigured. He was found by Tegan and Nyssa, companions of the Fifth Doctor. He had used the transmat himself, but a temporal distortion from the pod had caused him to arrive on Earth in a later time zone - that of 1983. On arriving, he had met the Brigadier - now retired from UNIT and teaching at a public school. In 1977, Tegan and Nyssa also encountered the Brigadier - newly arrived at the school.

They thought that Mawdryn was the Doctor, regenerated once again, and he went along with their confusion so that they would take him back to the spaceship in the TARDIS.

Having discovered that the Doctor was a Time Lord, Mawdryn wanted him to sacrifice his remaining regenerations to cure him and his colleagues of their mutation - one future life for each of them.

To force him to help, the mutation had infected Tegan and Nyssa. They aged when the TARDIS moved forward in time, and regressed to childhood when it went back in time.

The entire situation was being manipulated from behind the scenes by the Black Guardian, who wanted to see the Doctor reduced to mortal form. He had also employed a schoolboy named Turlough to kill him.

Both versions of the Brigadier had been brought to the spaceship by accident, and the Guardian ordered Turlough to prevent them meeting, but the boy failed to do so. They physically encountered each other just as the Generator was activated. Instead of the Doctor losing his regenerations, the temporal differential was shorted out and the resulting energy killed Mawdryn and his fellow scientists.

Shortly after the TARDIS departed, with Turlough now on board, the spaceship self-destructed.

Played by: David Collings. Appearances: Mawdryn Undead (1983).

• Third and final appearance by Collings in the series. He had previously played Vorus in Revenge of the Cybermen, and Poul in Robots of Death.
• In his novelisation of this story, Peter Grimwade names Mawdryn's race as Kastrons.
• "Mawdryn" is Welsh for "Mother", but Grimwade made the character name from marw (dead) and dyn (man).
• On audio Collings portrayed an alternative version of the Doctor.
• A regular performer with the BBC radio drama group, one of his best known TV appearances was as Silver in the cult series Sapphire & Steel. He also features in the final episode of Blake's 7.
• His voice work also included the English dubbing of the Japanese fantasy series Monkey.
• A film role of note is Bob Cratchit, in the 1970 movie adaptation of the stage musical Scrooge.