Over her 70-year reign, the Queen has met many world leaders from prime ministers to presidents - and even other monarchs.
And before meeting each one, it is said she receives briefing notes, advising her on their personalities and topics she should probably avoid talking to them about.
But when she was due to meet up with Queen Margrethe of Denmark, one royal author has claimed she advised her to steer clear of mentioning on very peculiar topic.
