'I watched my mum fall in love with 15-year-old Emmanuel Macron.'

It’s one of the most fascinating love stories of our time. And now Brigitte Macron’s daughter has shared what it was like to watch her mother fall in love with her 15-year-old student, Emmanuel Macron.

Tiphaine Auzière is now 34, but she was just nine years old when her teacher mother’s love for her then-student ended her family’s life as she knew it.

In a TV documentary Brigitte Macron: A French Novel which aired this week, Tiphaine said she, like so many others in the small town of Amiens, could see that the then-40-year-old literature teacher had fallen in love with the future French president.

"They were quite smitten and it was quite obvious between them and very difficult," said Brigitte's youngest daughter from her first marriage.

Tiphaine said the first time she'd heard of Emmanuel Macron, now 40, was when her older sister Laurence came home from their private school and said, "Mummy, there is a crazy boy in our class who knows everything about everything."

Brigitte's romance with Emmanuel continued to grow, and according to the film, when he was 16 years old his parents asked her to stop seeing their son until he turned 18.

Brigitte, now 65, reportedly replied, "I can’t promise you anything."

But the family took matters into their own hands, sending him to Paris to finish school.

Brigitte's marriage to her first husband, André-Louis Auzière, ended when he found out about the affair and left the family home.

A parents' divorce is often difficult for children, but Tiphaine only spoke kind words of the now-married couple, expressing how much they love each other.

Perhaps it's because the couple maintained contact for 13 years by distance before they married in 2007 that Tiphaine and others close to the pair do not doubt their bond.

"If I have to give a vision of love, it’s Emmanuel and mum," Tiphaine said. "When they are together, it is almost as if the world doesn’t exist."