100,000 BC - S1-E1
Character mistake: When Ian is trying to escape from the TARDIS in episode 1, he says, "He closed the door from over there, I saw him." It was in fact Susan who closed the door.
Character mistake: The miniaturized TARDIS crew never interact with the other characters in this story, because, as the Doctor points out, the 'giants' will be unable to hear them, as their voices will be on a different wavelength. So why does the Doctor later suggest using the telephone to try to call for help?
Character mistake: Despite being asked to memorise all the locations and war zone commanders, Zoe's photographic memory lets her down: her first words to the Mexican leader are 'Who are you?'.
Character mistake: The Doctor gets Jo to do some mathematics to distract her. At one point she says "49 x 2=88", when it actually equals 98, then she says that "adding 10 equals 108". (In other words, Jo (Katy Manning) fluffed her line, got one figure wrong, then went back to script...).
Character mistake: The Doctor (Patrick Troughton) makes one of the funniest fluffed lines in the entire history of Doctor Who in the final episode. With all sincerity he says "We'll all be dead soon, unless you switch over to the sexual air supply." (The word Troughton was probably looking for was "sectional.").
Remembrance of the Daleks - S25-E1
Character mistake: The gate to I.M. Foreman's scrapyard reads "I.M. Forman."
Character mistake: A Sensorite says, "Give my Doctor the congratulations," instead of "Give the Doctor my congratulations," in the fourth episode.
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.
Battlefield - S26-E1
Character mistake: The Brigadier asks the pilot if she speaks Czechoslovakian, even though Czech and Slovak are different languages.
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.
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