After the Spy Master unveils his CyberMasters to the Doctor, he proceeds to test them out by having one zap the other. The Master laughs as the shot CyberMaster regenerates, before immediately running away when a Dalek emerges from said regeneration and zaps the other CyberMaster. The Doctor explains: "That's the problem with regeneration. You never quite know what you're going to get!"
According to one account, the Master had the appearance of Roger Delgado while on Gallifrey. According to another, he had Anthony Ainley's likeness. According to another one, the one with James Dreyfus's appearance was the incarnation who ran away from Gallifrey.
While fighting to extend his life at the end of his regeneration cycle, many bodies were possessed by the Beevers incarnation, but all kept somehow reverting to his real being until he finally regenerated into the MacQueen one. Hence, these sections cannot be strictly chronological
