Capaldi Already Filmed Regeneration

Despite not leaving until the unfilmed Christmas special, Peter Capaldi claims to have already filmed the 12th Doctor's death, saying, "I did it the other day. It was a strange day. It was explosive. He goes out a fighter." How this will play out remains to be seen. There could be a David Tennant-style thing where he holds the regeneration in for a long time. Or perhaps the regeneration is stopped by something, only for him to get killed again in the next episode.