Over the years the Queen and her husband Prince Philip have dined with some of the most famous and most important people in the world.
They've thrown some incredible state banquets at Buckingham Palace, as well as enjoying some historical meals while visiting other countries.
But when they invite guests to more private dinners, there are a few strict rules people have to follow.
There's one particularly strict demand that Prince Philip makes of everyone who sits down to dine with him - and it's rather unusual.
According to royal author Brian Hoey, the Duke always decides what they talk about.
In his book Not in Front of the Corgis , he writes: "When Prince Philip gives a private dinner, he likes to decide the subject for conversation.
"One lady was dismayed to find she was expected to contribute on the subject of ‘deciduous trees,’ about which she knew absolutely nothing."
"If guests are not quite as knowledgeable as they should be, the Prince can become very touchy - but if someone is more expert than him it can just as easily ruin the occasion.
But there is a way to save yourself any embarrassment if you ever happen to be invited to dinner with Philip.
Brian explains: "Apparently the secret is to contact his office beforehand and find out his pet topics of the moment and learn just enough to be able to contribute intelligently, but not to upstage the host.
"Otherwise he can become 'less than pleasant'."
