The season limps to an end with The Invasion of Time. It limps due to being set a lot in a disused mental hospital doubling as the Tardis, plus being incredibly padded in to six largely dull episodes. It's Louise Jameson's last serial too, but her exit is done very badly

Having did that , there are lots of good things in this episode. The twist at the end of part four is awesome. The Chancellor and Castelan are great characters too.