This is one of the best Doctor Who stories ever. The whole episode is written so perfectly and is so satisfying. The Doctor having to confront a tragedy that’s a fixed point in time and not do anything about it? Which is already foreshadowed in Pompeii? Plus, Ten’s entire arc leading up to the Time Lord Victorious in a way that feels earned? Doctor Who doesn’t get darker or more interesting than this. This is a 60 minute special but not one minute is wasted. Just perfection.