While there are a number of protocols and rules that take place at Buckingham Palace, many people may not think anything of the type of cutlery used by the royals.

However, it has been revealed that there is one utensil missing from the Palace for a very good reason.

Etiquette expert William Hanson said that fish knives are a no-go at Buckingham Palace and are not used by royals.

He said: “There are two things: one is the class thing and fish knives are seen as down-market. But Buckingham Palace’s cutlery goes back to Georgian times and fish knives had not been invented then so they don’t have them by default.

“When fish knives came in at the end of the Victorian period they were seen as a little bit middle class, which was the class that boomed during the Industrial Revolution [and they] invented cutlery for everything.”

In his book on etiquette and manners, Just Good Manners, Hanson also says that when they were invented, a fish knife was a “social marker that the host was a touch common” and that the Queen Mother would instead eat fish with two regular forks.

It was also revealed that Queen Camilla would never be seen with the utensil, which was once mentioned in Sir John Betjeman’s 1958 poem How to Get On in Society.

In the poem, the fish knife is considered to be used by people who have not entirely mastered the right etiquette, with a famous line from the poem being “phone for the fish knives Norman”.

Speaking at the Cheltenham Literature Festival, sponsored by The Times and The Sunday Times, Princess Margaret’s former lady-in-waiting Lady Anne Glenconner said that Camilla once reacted when the utensil was offered to her.

According to Glenconner, the Queen was out for lunch with her sister Annabel Elliot, when a fish knife and an ordinary knife was offered.

Glenconner, 92, said: “The waitress came and asked, ‘Which knife would you want?’ and the three of us said, ‘Phone for the fish knives, Norman’.

“And the Queen, she knew all the words, everyone in the restaurant was just amazed.”