The Excelis trilogy is marked by the continual appearance of Anthony Stewart Head, ostensibly as a different character in each story, although by the end it becomes clear that all three characters played by Head are the same man.
He also played Doctor Who companion Bernice Summerfield's father, Isaac Summerfield, in Death and the Daleks, and he guest starred in the Big Finish Productions Doctor Who audio drama Excelis Decays.