The Trial of a Time Lord 5-8 (aka Mindwarp) - S23-E2
Continuity mistake: When Kiv wakes up in Peri's body, (s)he orders Crozier to kill the body Kiv was using before. Crozier responds that it's already dead, but in the previous shot the old body could be seen breathing.
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