The newlyweds emerged into the sunshine, and shared an embrace to the delight of the waiting crowd.

Meghan asked her new husband: "Do we kiss?" to which he replied with a discreet "yeah", according to lip reader Tina Lannin.

Ever since the Prince of Wales and Lady Diana Spencer delighted millions by sealing their marriage with the romantic gesture, royal newlyweds have puckered up in front of well-wishers in what is a defining moment of the day.

These rare displays of affection afford the public a glimpse into each relationship and the ease at which some, more than others, are willing to show their love for their new spouse.

Judi James, a body language expert, said it was a smart move for the new Duke and Duchess of Sussex to kiss early after their wedding ceremony.

"The timing of the kiss was perfect and it looked like Meghan's idea to do it on the steps, as she was the one who murmured to him," she said.

"It almost seemed like her theatrical experience may have influenced the decision to do it early, as the more time you wait the more tension and pressure builds up."

James said it was "a very Hollywood kiss".

"They just slightly leaned their heads to a right angle and Harry went for the lower lip which is popular on screen technique as it minimises the amount of damage done to the make-up," she said.

"It was a very clever way to ensure there were no problems and that it all went smoothly."

The traditional "first kiss" has become as much a part of a royal wedding as the ceremony itself.

When Charles and his new bride married on July 29, 1981, their kiss became one of the most enduring images in royal history.

The break from formality and royal protocol came in direct response to calls from the crowds waiting below the Buckingham Palace balcony.

At the time, Charles was reported to have said to Diana: "I am not going to do that caper. They are trying to get us to kiss." Then, she responded: "Well, how about it?"

However, as the young princess arched gracefully backwards, her veil flowing behind her in a fairytale pose, her husband appeared rather less at ease, creating a slightly stilted embrace.

Five years later, the Duke and Duchess of York followed in their footsteps, appearing to relish their wedding day "balcony moment".

A smiling and relaxed-looking Sarah Ferguson played to the crowds, putting her hand behind her ear, and appearing to mouth "what?" and "I can't hear" before leaning in for a kiss with her new husband.

In 2011, it was the turn of Harry's brother the Duke of Cambridge with his new wife, Catherine Middleton.

With the eyes of the world upon them, the couple's long-awaited kiss demonstrated confidence and spontaneity. To the delight of well-wishers waiting below, they kissed not once but twice.

To chants of "kiss, kiss, kiss", William and Kate shared a brief but loving kiss that failed to completely satisfy the crowds, who began calling for more just minutes later.

Once more the newlyweds obliged, to huge cheers from below.

Australian Associated Press