Prince Philip reportedly makes an unusual demand whenever he hosts private dinners at the palace.

Royal author Brian Hoey revealed in his book “Not In Front of the Corgis” that the Duke of Edinburgh is the one that decides what subject they would discuss during get-togethers.

During one occasion, a female guest became dismayed when she found out that she was expected to contribute on the subject of deciduous trees. This is because the guest didn’t know anything about it.

“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,” he said.

Luckily, there is a way for guests to deal with the situation without embarrassing themselves. One suggestion is to call Prince Philip’s office beforehand and ask what his current topic of interests are at the moment. This way, the guests can contribute to discussions intelligently without upstaging the Duke of Edinburgh.

According to Hoey, when the dad of four feels that he’s being upstaged, he tends to become less than pleasant.

Meanwhile, Prince Philip also dislikes being interrupted when he’s watching his favorite television shows. Even when his expected guests are the ones that pay him a visit, Queen Elizabeth II’s husband usually asks his doorman to give the guest a drink and to inform them that he would be out in a minute after dealing with urgent business.

According to the royal author, Prince Philip and Her Majesty’s third child, Prince Andrew, is the one who inherited the sneaky tactic from his father.

In related news, Prince Philip retired from royal duties two years ago. But every now and then, he still makes public appearances with the royal family. He was present at Prince Harry and Meghan Markle’s wedding on May 19 and Princess Eugenie and Jack Brooksbank’s nuptials on Oct. 12, 2018.

Prince Philip
Pictured: Prince Philip leaves St George's Chapel after the wedding of Prince Harry, Duke of Sussex and The Duchess of Sussex at St Georges Chapel on May 19, 2018 in Windsor, England. Getty Images/Gareth Fuller-WPA Pool