Revealing mistake: The Filer vs. Filer fight in the lab is very amusing, not only because of the several glimpses of the stuntman doubling for Filer, but also because of the way the "metal" railings around the set wobble as they slam into them.
Revealing mistake: In the UNIT tracking room, there is a flimsy railing behind the radar operators that Chinn knocks as Yates leads him off to the "direct" phone line, causing it to wobble badly. The Doctor then deals the railing another blow as he comes up to look at the console.
The Daemons - S8-E5
Revealing mistake: When the Brigadier crosses over to the RAF and the plane, you can see the plane is a model with a stick to control it just under the nose.
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