Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
How The Monk Got His Habit was a Doctor Who story pitched by Peter Harness to Steven Moffat shortly after writing the Series 9 two-parter The Zygon Invasion/The Zygon Inversion. The story would have been a one-parter and featured the modern Doctor playing a part in the origin story of the Monk, who would have been making his return to television.
The story was never produced, though Harness had already mused on potential casting, hoping to have Matt Berry play the Monk; he stated in 2020 that he had begun writing a novelisation.  Harness reflected in 2020 that in hindsight, his pitch "seemed completely insane". However, he also wistfully noted that the story "might have been fun" all the same.
The cold opening of the episode would have begun with the Monk listening to some disco records "one day in his TARDIS". Listening to the song "Ra-Ra-Rasputin" by Boney M, the renegade Time Lord suddenly thinks to himself "how hysterical it would be" to go back to czarist Russia and have the real Grigori Rasputin listen to the song. He does exactly that, only for the experience to drive Rasputin completely mad. This is enough to change history, averting the Russian Revolution of 1917 and consequently mess up the further course of human history. Terrified at what he has done, the Monk phones the Doctor and says: "I've made made a terrible mistake".
After the credits roll, the Monk would turn out to have contacted, not his contemporary, but the current Doctor; together, he, the Monk and his companion(s) try to put things to right. With it proving impossible to return the real Rasputin to normal, the Doctor's fellow Time Lord is eventually forced to regenerate into Rasputin's form and act out the rest of Rasputin's "correct" lifetime in the part of "the Mad Monk" — a role which would, the Doctor knows, rub off on him.
In 2020, seeing the extremely positive fan reaction to his unveiling the scrapped project during Doctor Who: Lockdown!, Harness released a prose piece described as the opening scene of the unfinished novelisation.
- Peter Harness on Twitter — "After the Zygons I pitched an origin story for The Meddling Monk called 'How The Monk Got His Habit'."
- Peter Harness on Twitter — "The vague basis for "How The Monk Got His Habit", from an email back in 2015"
- Peter Harness on Twitter — "Here's the similar discarded first page of a novelisation of [the Meddling Monk idea]"