Magister1971

A seller using the username Magister1971 once sold Giles a fake DVD of a missing Doctor X episode, Doctor X and the Caverns of Andostar. The DVD knocked out P.R.O.B.E.'s technology, allowing a Nolvox control node to be stolen from the Dr Smith shelf. (WC: Doctor X)

Notably, the alias "Victor Magister" had been used by when he posed as a vicar in Devil's End. (TV: The Dæmons, PROSE: Doctor Who and the Dæmons, Who Killed Kennedy, The Eight Doctors)

Behind the scenes

 * As "Magister" is the Latin term for "Master", the suggestion is that this individual was the Master. He could further be narrowed down to, who debuted on television in 1971. However, this was not explicit because the webcast was not licensed to use the Master.