Character mistake: When the Doctor is saying the decimals of Pi to avoid falling under the control of BOSS. He gets it wrong; he says "3.1416..." When it's actually 3.141592.
Continuity mistake: When Karra dies and turns back into her human/humanoid form she is wearing a black top that they did not wear as a Cheetah Person.
Battlefield - S26-E1
Character mistake: The Brigadier asks the pilot if she speaks Czechoslovakian, even though Czech and Slovak are different languages.
Revealing mistake: When the Doctor and Leela are confined to the officer's quarters, look at Leela's eyes after she sits down; one of her brown contact lenses has fallen out, revealing her real blue eye.
Remembrance of the Daleks - S25-E1
Continuity mistake: When the Doctor and Ace steal the military van they leave the doors open, but in the next shot when we see the van leaving Totters Lane the doors are suddenly closed.
Continuity mistake: The Doctor's hair goes from being messy and extremely curly in the TARDIS scenes to being combed and much less curly in the scenes set outside the TARDIS.
Continuity mistake: When the Doctor picks up the humanoid skull his hat is looking normal but in the next shot the brim of his hat is folded down and completely flat. In the next shot it's back to not folded again.
Character mistake: When the Brigade Leader shoots the Primord, he noticeably closes his eye. He is supposed to be a high ranking well trained officer.
Castrovalva - S19-E1
Deliberate mistake: The newly regenerated Fifth Doctor is wearing completely different shoes than the Fourth Doctor did in the previous story. This is deliberate. The boots worn by the Fourth Doctor were actually privately owned by actor Tom Baker. Still, a mistake but this is why.
The Sontaran Experiment - S12-E3
Continuity mistake: In Episode 2, when the Doctor calls Harry from the Control Room and Harry enters the room next to the Cryogenic Chamber, there is an oblong yellow panel next to the door. It extends from about Harry's waist line to about 200mm below the top of the door. But in Episode 3, when Noah calls Vira from the control room part way into his transformation, and everyone runs into the adjacent room, the panel is mounted differently. It now extends from about Harry's mid-torso, to the top of the door frame. (00:03:35 - 00:09:32)
Continuity mistake: In "The Deadly Assassin" the Doctor's blood is red but in "State of Decay" his blood is suddenly dark blue. Then it's back to being red in "The Two Doctors."
Answer: It was never destroyed on-screen; it was intact at the end of the TV movie, and destroyed by the start of the 2005 series. It was destroyed in the novel "The Ancestor Cell," but in a completely different manner to what happened in the series.
DaveJB