The couple have moved around, living in Birmingham and London before finally settling in the small town of Lichfield, in Staffordshire.
It was there, first in a spare room, then in an office in their garden that Mr Stone began piecing the evidence together.
He said his wife had buried what had happened to her for a long time, which he says is the case for many survivors around the world.
“The majority of them have deeply, deeply put this in a box and buried it away,” he said.
When he contacted former employees of Al Fayed, he said: “I can’t tell you how many times I had someone say something like, ‘you’ve no idea how long I’ve waited for this email or this text. I’ve waited 25 years for someone to ask me about this.’
“Things had tried to come out about him before, [but] they never landed and he was able to swat them away.”
Since the documentary, the team have been “inundated” with more survivors coming forward, and Mr Stone believes there are now more than 100 of them.
