From the only TV reference to Merlin, it's unknown; it could be Eighth, Ninth, Tenth, Eleventh, or an incarnation the audience hasn't seen yet. That reference makes a few things clear: 1. Merlin was known to change his appearance (suggesting that more than one incarnation was Merlin); 2. The Seventh Doctor's appearance was new to Ancelyn, though Ancelyn still recognised him as Merlin; 3. The note left (in Arthur's armour) for the Seventh Doctor was from a future Doctor. Retroactively, the idea of Merlin being an as-yet-unseen incarnation of the Doctor is further made possible by the renewed regeneration cycle bestowed upon the Doctor in "The Time of the Doctor", which adds potentially any of nearly a dozen more incarnations who could become Merlin.
From the other media, it's a bit complicated. There are three separate stories that aren't necessarily contradictory, but don't fit together completely naturally. To try to integrate everything:
Later, the Eighth Doctor meddled with the TARDIS and got himself trapped in an infinite loop, becoming Muldwych. Because the Doctor no longer had to become Muldwych for him to exist, when Mulwdych escaped the infinite loop, he was essentially an alternate future of the Doctor, with his own separate existence from the Doctor's 'normal' future self. So, both versions had been the Merlin Doctor, before they diverged into separate incarnations/people.
Finally, either the Eighth or Ninth Doctor later met Arthur as an adult, and was recognised as Merlin.
Of course with the background of the Eighth Doctor Adventures novels changing the Doctor's past, eliminating and restoring the multiverse of alternate histories, and so on, maybe we aren't meant to fit the different stories together.
See Also Edit
- ↑ "Battlefield"
- ↑ Possibly the origin of the idea that Merlin "aged backwards", growing younger instead of older.
- ↑ 'One Fateful Knight', from Short Trips: The Quality of Leadership
- ↑ "Birthright" (Virgin New Adventures novel #17)
- ↑ "Happy Endings" (Virgin New Adventures novel #50)
- ↑ IDW comic Fugitive