Darisdale Major

The Major helped The Master, under the "cunning" disguise of McMaster, to complete Masterplan Q. He denied the Third Doctor and Jo entry to the Darisdale research station of which he was major of, so McMaster wouldn't be discovered.

He then joins McMaster and tells him that he can count on the loyalty of his men. The Major is presumed to be arrested when Jo arrives with reinforcements, which are known to arrest the corrupted staff.