Hacker is seen opening a door clearly marked PRIME MINISTER but as he starts to go through the door is blank.
When Major Saunders visits the minister at his home, shadows of boom mic movements cross their faces during closeups of both men.
Sir Humphrey's claim that his believing in widely changing government policies would require he become "a stark, staring, raving schizophrenic" confuses schizophrenic and multiple-personality disorder. This was actually a widely held misconception at the time.