This prequel to the 50th anniversary special is itself something special. It brings back to the show the Doctor who had the least time on the screen, Paul McGann’s Eight Doctor. And it gives us a glimpse of the impact of the Time War between the Time Lords and the Daleks, the extent to which the former had become no better than the latter in seeking to defeat them, and how the Doctor moved from refusing to get entangled in it to choosing (with the help of the Sisterhood of Karn) to become a warrior. That setting was a nice connection with the classic series.
There is a wonderful Biblical allusion, when the Doctor says “Physician, heal thyself.” And as we hear the words “Doctor no more” we see a glimpse of a relatively young John Hurt, and thus are given an indication that the missing part of the Doctor’s story, which we hadn’t seen, stretched over a significant period of time.