"The memory of that night will stay with me forever."

Her death was a global story, sparking heartbreak across the world, but now a firefighter who was at the scene of the fateful crash has revealed what she said to him moments before she went into cardiac arrest.

Xavier Gourmelon was a firefighter who was part of the emergency response to the crash in Paris' Pont de l'Alma tunnel on August 31, 1997.

Gourmelon previously explained that he had no idea who Diana was, and initially believed she wasn't seriously injured as she was conscious and had her eyes open.

He said that he told her to stay calm while she was still in the vehicle, before she said: "My God, what's happened?"

"I massaged her heart and a few seconds later she started breathing again," Gourmelon previously told The Sun.

"It was a relief of course because, as a first responder, you want to save lives — and that's what I thought I had done. 

"To be honest I thought she would live. As far as I knew when she was in the ambulance she was alive and I expected her to live.

"But I found out later she had died in hospital. It was very upsetting."

He continued: "I know now that there were serious internal injuries, but the whole episode is still very much in my mind.

"And the memory of that night will stay with me forever. I had no idea then that it was Princess Diana.

"It was only when she had been put into the ambulance that one of the paramedics told me it was her."

Diana was declared dead at 4am Paris time at Pitie-Salpetriere Hospital, despite doctors' best efforts to save her.