i'm just watching this now on SCREAM in Canada,and I can't believe that Tom Baker is one of the baddies!! Didn't realize it until the mutant started to speak and I looked up and ,sure enough, it was Tom! Great flick with Donald Pleasance by the way.
If you're surprised by Tom Baker's appearance in this I strongly advise you get hold of a copy of Pasolini's early 70's version of the Canterbury Tales. I also strongly advise you avoid any potential spoilers because when the moment comes, for a while at least, you'll not be able to look at the 4th Doctor without that image entering your mind.