That’s not to say that there haven’t been rule breakers.

The most stoic of couples was certainly Queen Elizabeth II and Prince Philip, who kissedmaybetwice in public.

Here are rare royal PDA moments that you don’t want to miss.

Prince Charles and Princess Diana posing

His Royal Highness and Ms. Markle became engaged in London earlier this month.

Prince Harry has informed Her Majesty The Queen and other close members of his family.

Prince Harry has also sought and received the blessing of Ms. Markle’s parents.

Prince William and Princess Catherine BAFTAs

The couple will live in Nottingham Cottage at Kensington Palace."

Oh how times have changed since.

For instance, 1985 sawCharles both hug and kiss Dianaafter a polo match held at Cirencester Park.

Prince Harry and Meghan engagement

That same year, the two exchanged a kiss that of course was captured by cameras.

Though they weren’t the most affectionate, Diana and Charles seemed to connect when polo was at play.

Still, she and her new husband practiced extreme measures of monarchical rule, even during their honeymoon.

Prince Charles and Princess Diana kissing

Elizabeth stunned in a blue dress with a matching coat, and the two made their way to Balmoral.

Clearly, the polo field has a PDA power that the royals can tap into.

As it turned out, the rain was a welcome and rather symbolic downpour.

Queen Elizabeth and Prince Philip honeymoon

It was the gestures between her and Harry, however, that had people watching closely.

Of course, many royal watchers know that things didn’t go so smoothly for the couple.

As far as William and Catherine were concerned, the two appeared business as usual.

Prince William and Princess Catherine kiss

“This dynamic cannot be unseen,” Rosas said while analyzing the differences between the two couples.

[Kate’s] posture is normal royal protocol."

Harry and Meghan in Australia

Prince Philip kissing Queen Elizabeth

Prince Harry and Princess Meghan during Thanksiving

Prince William and Princess Catherine Jamaica

Duke and Duchess of Windsor and Sussex walking

Princess Diana and Prince Charles dancing

Prince William and Princess Catherine at Wimbledon

Royal family portrait