However, Prince William is known to bend them a little bit when he feels it's necessary. Whether it's going against wedding traditions or always ensuring that his family stays together when they fly, he has often ripped up the royal rule book.
But there's another royal rule that William will break - and it's all to do with selfies.
In the past, royals have refrained from taking photographs with fans and well wishers, but social media was flooded with images of the Prince recently following his undercover charity work for The Big Issue.
William was spotted in London selling copies of the magazine, and many took to Instagram to share their selfies with the royal.
Taking photos with the public is said to be frowned upon by the Queen, with Meghan Markle once telling fans in 2017: 'We're not allowed to do selfies.'
Around the same time, one guest at a Buckingham Palace garden party told Insider that attendees were warned against it as it could be seen as disrespectful.
They said: 'The one thing they talked about a lot was no selfies, and the reason was that they didn't want people turning their backs to the Royal Family and the Queen. And that was very important to them.
'You do not turn your back on the Royal Family, and you do not attempt to walk up and talk to them.'
Royal commentator Victoria Arbiter also added that the royal family would 'always rather have a personal interaction' and that they're also tricky from a 'security standpoint'.
So how did people manage to get a selfie with William this month?
In their coverage of the Duke's undercover work, The Big Issue reported that he allowed photographs on one condition - that they support his charitable endeavours.
They said: 'Lots of people want to shake hands, snap a selfie and have a chat, which William allows – only if they buy a magazine, of course.'
So now you know!
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Jadie Troy-Pryde is News Editor, covering celebrity and entertainment, royal, lifestyle and viral news. Before joining the team in 2018 as the Lifestyle and Social Media Editor, she worked at a number of women’s fashion and lifestyle titles including Grazia, Women’s Health and Stylist, and now heads the Marie Claire UK news desk.
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