A slap, a 24-year age gap, and the controversy surrounding Emmanuel and Brigitte Macron.

It was the alleged slap heard, and felt, around the world.

This week, video captured by Associated Press showed what appeared to be an altercation between French President Emmanuel Macron and his wife, France's First Lady, Brigitte Macron.

In the clip, a plane door slides open to reveal Emmanuel locked in animated conversation with someone not quite visible.

That would change soon enough.

Two red sleeves came out of nowhere and forcefully pushed the leader's face away. Emmanuel recoiled and, realising cameras were on him, turned and waved.

Moments later, Brigitte Macron, walks into view.

The moment, which has since gone viral, was captured as the couple arrived at Hanoi Airport, in Vietnam, for the start of a tour of Southeast Asia.

Brigitte Macron appears to slap Emmanuel Macron. Post continues after video.

Instead of raising awareness about geo-political relationships, the "slap" has instead put the couple's relationship under a new spotlight.

And it's not the first time…

How did Emmanuel and Brigitte Macron meet?

Emmanuel and Brigitte Macron's relationship had an unusual beginning and has long been the subject of fascination and controversy in France.

Their story began in 1993 at Lycée La Providence, a prestigious private school in France, when 15-year-old Emmanuel was a student and 39-year-old Brigitte Trogneux was a drama teacher.

Although they did not have classes together, the pair met while working together on a play, an adaptation of "The Art of Comedy". They collaborated every Friday night for months.

Emmanuel and Brigitte Macron. Image: Getty.

According to reports, Brigitte was impressed by Emmanuel's intellect. At the time, she was married to banker André-Louis Auzière and had three children, including a daughter — Laurence Auziere — who was in Emmanuel's class.

Emmanuel's parents, Jean-Michel Macron and Francoise Nogues-Macron, were unaware of the developing relationship. They instead believed their son was romantically involved with Laurence.

When Emmanuel and Brigitte's affair came to light, they were shocked.

According to Anne Fulda, author of Emmanuel Macron: A Perfect Young Man, Emmanuel's parents met with Brigitte and requested she not see their son until he was an adult. She reportedly refused to "promise anything."

Francoise is said to have told Brigitte, "Don't you see? You've had your life. But he won't have children with you."

In an attempt to separate the pair, Emmanuel was sent to Paris to complete his final year of his education.

But the two maintained contact.

Brigitte confirmed to Paris Match that Emmanuel made a vow to marry her when he was just 17 years old, and promised to come back and find her after he was sent to the capital.

"You cannot get rid of me. I will come back and marry you," he is quoted as having said.

The pair would marry in 2007, more than a decade after they first met.

Emmanuel was 29 and Brigitte was 54 years old. Their marriage occurred one year after Brigitte's divorce.

Fast forward another decade to 7 May 2017, and Emmanuel would become President of France.

What have they said about the slap.

Headlines have been running rampant after the incident in Hanoi, with the website of the Le Parisien, a daily newspaper, asking, "Slap or 'squabble'? The images of Emmanuel and Brigitte Macron disembarking in Vietnam trigger a lot of comment."

Emmanuel has been quick to dismiss the alleged altercation and likened the worldwide reaction to "a sort of geo-planetary catastrophe".

He insisted the moment was nothing serious.

"We are squabbling and, rather, joking with my wife," he told reporters this week.

Hear what The Quicky had to say about the slap. Post continues below.

It was a sentiment echoed by his office in a statement.

"It was a moment where the president and his wife were decompressing one last time before the start of the trip by horsing around. It's a moment of complicity. It was all that was needed to give ammunition to the conspiracy theorists," his office said.

Despite the latest controversy, the pair are once again presenting a united front; it's a strategy that has served them well through Emmanuel's political rise.

Feature image: Getty.