Meghan Markle and Prince Harry caused quite a stir when they appeared out and about together in Toronto holding handsaccording to People. Holding hands may not seem like something that should make headlines, but in the British monarchy, public displays of affection are a big no-no.

Harry's older brother, Prince William, and his wife, Duchess Catherine, are rarely photographed in public holding hands because the couple technically work as representatives of the British monarchy, according to royal etiquette expert Myka Meier, People reported.

"The couple are likely to show very little PDA, if any, to remain professional during their designated roles abroad," she said of William and Catherine.

But Harry and Markle’s PDA means something to Meier.

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"I believe an engagement is imminent," she said to People. "I think to show PDA at such a highly publicized public event would be a very conscious decision by Prince Harry, and shows the seriousness of the relationship. Meghan would very much have taken his lead under the circumstances."

According to Meier, there is "no formal protocol" against affection in public, but it is rare to see an unmarried royal pack in the PDA.

“It certainly makes a statement,” she said. “To show PDA as a representative of the British monarchy at such an official event says everything! Rarely in the past have we seen unmarried royals showing PDA with significant others at a public event — it’s a sure sign that things are as serious as they could be without being engaged.”