The Royal Family is a global institution and everyone from the King to The Princess of Wales is expected to follow protocol - but, like with everything, exceptions can be, and have been made.
According to the Royal Family website, it suggests that upon meeting royalty, men should bow from the neck and women should dip into a small curtsey.
And while there are also suggestions on how to address royalty, there have been a number of times during official state visits when friendship has broken down the barriers and allows the public to witness some very memorable moments.
The best example was during the first state visit of former US President Barack Obama and First Lady Michelle Obama to Buckingham Palace in 2009.
While standing next to each other at a small reception, Michelle opted to put her arm around the monarch.
Meghan Markle 'to unleash her own memoirs' as Prince Harry's drops next weekTo everyone's astonishment, the Queen reciprocated the gesture and placed her gloved hand on the former First Lady's back. Protocol dictates that you should refrain from touching the royals, unless they initiate the contact.
In 2018, Michelle spoke about why she put her arm around the Queen and what happened afterwards in her best-selling memoir, Becoming.
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She said: "The Queen glanced down at the pair of black Jimmy Choos I was wearing. She shook her head. 'These shoes are unpleasant, are they not?'
"She gestured with some frustration at her own black pumps. I confessed then to the Queen that my feet were hurting. She confessed that hers hurt, too.
"We looked at each other then with identical expressions, like, when is all this standing around with world leaders going to finally wrap up? And with this, she busted out with a fully charming laugh."
The former FLOTUS explained that she did what was "instinctive" to her by affectionately placing her hand across the Queen's shoulder, unaware that she was "committing what would be deemed an epic faux pas".
She added: "If I hadn't done the proper thing at Buckingham Palace, I had at least done the human thing… I daresay the Queen was OK with it too, because when I touched her, she pulled closer, resting a gloved hand lightly on the small of my back."
"I did what's instinctive to me any time I feel connected to a new person...[We were just] "two tired ladies oppressed by our shoes."
The late Queen’s close confidant and dresser, Angela Kelly also recalled the interaction in her book, ‘The Other Side of the Coin’.
Harry and Meghan convinced 'royals were against them' after New Year photo snubShe wrote: "The Queen has the ability to make everyone feel so relaxed that sometimes it feels instinctive to be tactile with her.
"Much has been made about the meeting between Michelle and Her Majesty when an instant and mutual warmth was shared between these two remarkable women, and protocol was abandoned as they stood closely with their arms around each other's backs."
Kelly continued: "In reality, it was a natural instinct for the Queen to show affection and respect for another great woman and really there is no protocol that must be adhered to."