10 Doctor Who Mysteries You Didn't Know Were Answered
8. When Did Ace Leave The Seventh Doctor?
Because Doctor Who went off the air in 1989 and never returned until 1996, Ace's departure was never depicted onscreen.
The original intention was reportedly to leave Ace on Gallifrey, where she would train to be a Time Lord. However, there are other tellings of the day the Doctor and Ace parted company in the expanded universe.
The 2020 novel At Childhood's End recounts the Seventh Doctor and Ace's last day together, in parallel with her first meeting with the Thirteenth Doctor. While the canonicity of that novel is now thrown out of whack by The Power of the Doctor, you can still sort of make it fit if you squint hard enough.
However, it's Tales of the TARDIS that gives us the most definitive date for the Doctor and Ace parting company in televised Doctor Who. Discussing their last day together in the Memory TARDIS, the Doctor states that "the Rani was up to her old tricks."
Given that the only time Seven and Ace faced the Rani together was in the 1993 charity special Dimensions in Time, we can definitively call that Ace's final story.
And if you've ever seen Dimensions in Time, you can completely understand why Ace would want to get shot of the Doctor soon after.