The Dalek Invasion of Earth - S2-E2
Revealing mistake: When Barbara is throwing her bombs, she grabs the window frame in front of her, which wobbles alarmingly.
The Dalek Invasion of Earth - S2-E2
Revealing mistake: In episode 1, one of the windows on the TARDIS is leaning in, but by the time we get to episode 6 it has managed to fix itself. Also when the bridge falls down you can see the poster through the gap, showing that there is no back to the TARDIS.
The Dalek Invasion of Earth - S2-E2
Revealing mistake: When Barbara, Jenny and Dortman are running through the deserted streets of London, in the very last shot, if you look to the left of the screen, you can see some people walking down the street.
The Dalek Invasion of Earth - S2-E2
Revealing mistake: When a rebel throws a bomb from the second floor of the Dalek saucer, notice it explodes too early and in the wrong place.
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