I feel like the Mirror reporting it now is because the rumor that Bradley would be back as the First Doctor has been floating around for months now, and part of that rumor included him being locked in that vault Capaldi was fretting over this episode. Now the episode aired, and there was indeed a vault, and Capaldi even suggested that, if something happened to it, he would immediately get a message on his Psychic Paper. That (along with hinting at that era with Susan's photo) definitely seems to hint that the rumor was true, which meant that the Mirror was more comfortable reporting it.
My theory: what if, like I said earlier when the first clips of the episode were posted online, Bill really is Susan?
The hints:
- The picture of Susan on Capaldi's desk, and him looking at it (with the camera lingering on it) when he mentioned he 'noticed her'. Now, it could be that he just noticed her because he can never help being interested in 'companion-types', but Bill even mentioned that there were others listening to his lectures that weren't supposed to be there, and yet he singled her out.
- The name 'Bill' could be a hint towards 'Bill/Billy Hartnell', which is what William H. called himself, and his closest friends as well.
- The Doctor always said that he would come back for Susan one day, and yet he never did (on tv). At some point, some writer was going to do it. What if the real reason Capaldi is there is to keep an eye out for Susan/Bill, in cooperation with his former self (Bradley), and that the First Doctor is hiding in that safe for as of yet unknown reasons while 12 is keeping a close watch on Bill? The finale would involve Bill learning who she really is, and her finally getting closure with the Doctor - especially the first one, which is the one she has the closest emotional relation with.
- If they're going to bring back the First Doctor, him promising to go back for Susan but never doing it is pretty much the biggest thing that's left hanging from his era. The only thing he never really got to do on tv, and the only thing left that really mattered.
- Capaldi always said he'd want to meet Susan again.
I'm not willing to bet 100 bucks on this theory or anything, I'm just having fun guessing here. But I'll bet $5,-. Why not.
We all know Moffat will want to go out with as big a bang as possible. At the end of this, he'll have done a multi-Doctor special, he'll have done his entire River arc, he'll have done three regenerations, a multi-Master special, the true return of Davros, a female Master, all the classic Doctors in reused footage, the regeneration of McGann, the Time War, an actual secret Doctor in that war, a full return to Gallifrey, the moment Doctor 1 and Susan first stole the Tardis....
I wouldn't put it past him to go all the way back to the first loose end of the series and finish up the Susan story for his grand finale. Why not.
