However, perhaps it’s a surprise that Whovians should have seen coming. With the help of time travel/looking at old YouTube videos, you can see that showrunner Steve Moffat teased Simm’s return way back in November 2015.
When asked about regenerating the Master into Michelle Gomez’s Missy at that year’s Doctor Who Festival, Moffat said that although the character had changed, “there’s no guarantee you don’t see John Simm again”. He went on to speculate there could be a multi-Master storyline with several evil Time Lords appearing at once.
““The Doctor experiences the universe out of sequence; it doesn’t mean you can’t have John Simm back as the Master. John Simm meets Michelle Gomez – oh dear Lord the children!” he said.
Who writer Mark Gatiss, who was also on the panel, picked up on the idea: “The Three Masters! Geoffrey Beevers!” he exclaimed, referring to the third actor to have played the Master, in 1981 Doctor Who serial The Keeper of Traken.
So, not only does this clip tell us Simm’s return was always in the back of Moffat’s mind, but it also suggests that the Master could team up with Missy. And perhaps even more regenerations of the Doctor’s foe.