Andrew Cartmel had time to take a more considered approach to the twenty-fifth season than he had to the twenty-fourth. After viewing a number of highly-regarded stories from the series' past, including season thirteen's The Seeds of Doom and season fourteen's The Talons of Weng-Chiang, he formed the view that the essentially serious and dramatic approach of earlier eras had been rather more effective than the relatively light-hearted and comedic one of Sylvester McCoy's first season. He discussed this with John Nathan-Turner and they decided that the departure of the somewhat lightweight character of Mel and the arrival of the strong, streetwise Ace should mark the start of a more general shift of emphasis back toward that more serious and dramatic style.
Another move that Cartmel was keen to make was to introduce a greater degree of mystery into the Doctor's character. He felt that over the years there had been too much revealed about the initially enigmatic time traveller's background, and that this had considerably lessened the appeal of the character. With Nathan-Turner's approval, he would therefore brief the writers of the twenty-fifth season to include in their stories some elements casting doubt on aspects of the Doctor's established history and on the true nature of his character.
This was very much in line with McCoy's own thinking about the role. His initial instincts had been to interpret it in a humorous way - most of his previous acting experience having been in comedy - but as he had settled in he had realised that it would be better if he played it much straighter.
The first fruits of this revised approach were to be seen in the new season's opening story, which kicked off the series' twenty-fifth anniversary year with the return, once again, of the Doctor's oldest adversaries.
The Greatest Show in the Galaxy continued the approach begun earlier in the season of depicting the Doctor as an enigmatic manipulator of events with a distinctly mysterious past. He visits the Psychic Circus having apparently guessed that it is a cover for the Gods of Ragnarok, whom he describes as old enemies - despite the fact that they have never before been mentioned in the series.
Ace, meanwhile, is left to do much of the detective work and to handle most of the action scenes. These trends would be continued in the following season, when the Doctor - and the series as a whole - would become even darker in tone and an even greater emphasis would be placed on Ace. What no one at the time could have known was that, after more than a quarter of a century of adventures, the series would soon be facing a very uncertain future.