The latest episode of Doctor Who, "The Tsuranga Conundrum", saw Jodie Whittaker's Doctor discard a promise made by Matt Smith's incarnation. Every version of the Doctor is very different, of course; the magic of regeneration is that it gives Doctor Who a unique ability to continually reinvent itself.
Back in the Matt Smith era, the Eleventh Doctor essentially saw himself as something of a cosmic event. In his very first episode, "The Eleventh Hour," the Doctor called defeated villains the Atraxi back to threaten them with knowledge of his long past and the evocative phrase, "Basically, run." The Doctor's mystique and legendary status became a recurring theme throughout the next two seasons - culminating in "The Wedding of River Song." In that episode, the Doctor finally realized that his legend was too great. After faking his own death, he declared "I got too big. Too noisy. Time to step back into the shadows." For the most part, the Doctor has been true to this promise since 2011; he deleted himself from history, and he kept his head down (as much as he could). That is, until "The Tsuranga Conundrum."
The latest episode sees the Doctor and her friends arrive in the 67th century, a period in time that's been relatively unexplored in Doctor Who canon. There, the Doctor delights in the fact that she's mentioned in the Book of Celebrants, which is presumably a record of all the most distinguished figures in Earth history. New character General Cicero is featured in it, and she recognizes the Doctor's name too, remembering she's the subject of an entire chapter. "I'd say it was more a volume than a chapter," the Doctor brags.
This is a surprising character twist. Previous episodes had suggested that Jodie Whittaker's Doctor was rather more like Patrick Troughton's incarnation than Matt Smith's; a subtle character who preferred to operate on the sidelines rather than draw attention. In "Rosa," for example, the Doctor encountered a time-traveler who could potentially have heard of her - and carefully avoided revealing her identity to him. What's more, until "The Tsuranga Conundrum" the Doctor had seemed rather more collaborative than "take-charge," preferring to work alongside others to issuing orders. In contrast, in this episode, she makes minimal effort to hide her legacy and quickly establishes her authority (while the Poirot joke is an amusing line, it also subtly demonstrates that she's the one with the power to summon everybody in the first place). From that moment on, the Doctor is in charge.
In-universe, there's a fair enough reason for why there'd be books written about the Doctor despite the Time Lord being written out of history. Indeed, as already seen in the series, some of the great races intuited a gap in their historical records and posited the existence of the Doctor. The Daleks were the first to achieve this, but there's no reason to believe others didn't do the same - and, sooner or later, the expanding human race would have started to hear rumors of this enigmatic wanderer. Eventually, historians would notice the same gaps in their own records; in fact, given the extent of the Doctor's involvement with Earth, it's probable that human history had more gaps than any other race's.
Of course, the bigger question is how this will affect the rest of Doctor Who season 11. Will the Doctor forget the lessons of the Matt Smith era and become a living legend once again? If so, this is sure to change the new dynamic about the TARDIS; the Doctor's new friends are unlikely to appreciate the ego, the arrogance, and the grandeur.
Whatever the truth may be about the Doctor's entry in the Book of Celebrants, a promise of the Matt Smith era - that the Doctor would no longer stand in a cosmic spotlight - has come to an end. It will be fascinating to see how Jodie Whittaker's 13th Doctor - and Doctor Who as a show - handles her own status.