The rules of the tiebreaker game aren't explained before it takes place, as if it's assumed that the contestants know how to play it without instruction. However, it's possible that the rules were explained during the recording, but omitted from the broadcast for time.
Joint 5th in the BBC-only chart, tied with an edition of Nine O'Clock News (1970) that same evening, with both being watched by 9.35 million viewers.