Character mistake: When Mrs. Slocombe volunteers to sing while Captain Peacock plays piano, Mr. Humphries responds that he didn't know she could sing, even though the department staff has been involved in many musical numbers over the series.
Character mistake: Mr. Lucas got himself in an embarrassing situation 'straightening the seams' of Mrs. Slocombe. Humphries passes by saving him by telling him that Mr. Granger wanted to talk to him, but he does it by saying "Griffin wants you." Wrong name. (00:07:45)
Answer: That wasn't possible in 1972. Until recently squatting was a civil offence in the UK, not a criminal one, and removing squatters was a complex and time consuming business.