A funny story Liz Sladen shared on "The Sontaran Experiment" DVD.
Kevin Lindsay (the Australian actor who played "Styre") had a heart problem so found it difficult to climb up & down the hill so decided to just stay there by himself whilst the others went down for breaks.
He also found it easier to just remain in full costume.
One day they came back up & asked if he was alright & he said, "Yes, I'm alright but but a young lady who was walking her dog just came by & got the fright of her life."
Obviously, for some people, Dr Who monsters looked convincing enough...
