Former RAF Squadron Leader, Graham Laurie, who used to work for the royals told Hello Magazine’s A Right Royal Podcast: “Interestingly, we flew all four: the Prince, the Princess, Prince William and Prince Harry, up until Prince William was 12 years old.

“After that, he had to have a separate aircraft and we could only fly all four together when they were young with the written permission of Her Majesty.

“When William became 12, he would fly normally in a 125 from Northolt and we would fly the 146 out with the other three on.”

It is still unclear whether George will be the one travelling solo or William.

Other peculiar travel rules for members of the Firm include not eating certain foods to avoid any case of poisoning.

The royals, particularly the monarch and the Prince of Wales, also travel with bags of their blood type in case of an emergency as well as their own doctor.

Lastly, another essential item the royals usually travel with while abroad is a black outfit as a precautionary measure for the purposes of mourning.

Famously, the late Queen Elizabeth was touring Kenya in 1952 when she found out George VI died and she had become Queen. However, she did not have a black outfit with her which meant a member of staff had to deliver one to wear as soon as she touched down in the UK.