Why William and Kate can't help but break royal protocol when it comes to being 'romantic' in public

The Prince and Princess of Wales are often quietly tactile in public, and many royal fans enjoy seeing how affectionate the pair are.

William and Kate have been married for 12 years, and share three children together - Prince George, Princess Charlotte and Prince Louis. 

For members of the royal family, there are a number rules they are expected to follow - especially when it comes to royal etiquette at official engagements.

While there is no set law, there is the unspoken rule for royal couples not to engage in excessive PDA, and as such kissing or holding hands in public is a rare sight.

However, William and Kate have a secret way to show their love and affection for one another, which is subtle enough that they're technically not breaking the rules. 

Eagle eyed royal fans may have noticed the pair looking longingly at each other at events. But body language expert Judi James has weighed in on the royal couple's PDA and their small signs of affection. 

The Prince and Princess are private people and keep their personal life to themselves, but when they do show affection, Judi believes it is 'inclusive' and a way to include onlookers. 

She explained to the Express: "William and Kate have been keeping royal fans, and each other, supplied with a stream of romantic gestures, tie-signs and touch rituals since they first married, but their technique seems to be driven by inclusion.

"We can see they are a romantic and in-love couple but they never allow their body language rituals together to exclude the viewer."

Though the couple may not hold hands in public, the tender moments and 'signals' are a nod to their romance and close bond. 

Judi continued: "Subtlety is vital for their public role and as royals, they provide signals that they are a strong couple, but that they maintain an even, steady emotional trend rather than a soap opera of passionate highs and lows.

"When they enter one another’s personal space on tours and visits, William, in particular, seems to be unable to avoid breaking what often seems to be his own rules of non-tactile public behaviour and intensifying the romance of the moment via gestures like this little nuzzling kiss of her hair."

The expert claims that these gestures are 'more for [William] than [Kate]', adding that as the Prince approaches his wife he becomes 'motivated by the desire to get even closer.'

How sweet!