Princess Diana's friend Rosa Monckton praises William for 'standing up' for mother over Bashir interview

Video report by ITV News Royal Editor Chris Ship

Princess Diana's close friend Rosa Monckton MBE has praised the Duke of Cambridge for "standing up" for his mother after he welcomed an investigation into the BBC's Panorama interview.

Prince William described the independent investigation into Martin Bashir’s interview with his mother as a “step in the right direction” and is understood to have “tentatively welcomed” the move.

Speaking to ITV News' Royal Editor Chris Ship, Ms Monckton said: "Any son would want to stand up for his mother in such circumstances".

She added: "But for him [William] and for Kensington Palace to issue a statement [...] I think shows how deeply involved he has become in this story and about how his mother was treated."

A close friend and confidante of Princess Diana, Ms Monckton also welcomed the investigation - to be lead by retired judge, Lord Dyson.

"I think it's very important that we look at it 25 years on," she told ITV News.

"It did change the course of history."

In the explosive interview 25 years ago, Diana famously said: “Well, there were three of us in this marriage, so it was a bit crowded.”

Princess Diana listens to her friend Rosa Monckton as she gives a speech in 1993. Credit: PA

Ms Monckton claimed the Princess was "coerced" into giving the interview, she claims, in a "dishonest way"

The charity campaigner claimed "fraudulent documents" were used to "persuade" Princess Diana into taking part.

Earlier this month the TV graphic designer who was asked to create fake bank statements to help secure the interview claimed he was made a “fall guy” by the BBC.

The BBC says Diana had written a note saying she did not see the false bank statements and they played no part in her decision to give the interview.

Reflecting on the impact of the interview back in 1995, Ms Monkton told ITV News she noticed a change in her friend Princess Diana at the time Mr Bashir was reaching out to her.

"She was jumpy, she was edgy, she thought she was being followed. I mean really, extraordinarily different.

"Everybody knew something was wrong but none of us could put a finger on it."

Ms Monkton said had she known Princess Diana was planning on giving the interview, she would have advised her friend not to do so.

"She did regret it," Ms Monkton said.

On the impact of the interview, Ms Monkton said Princess Diana's divorce from Prince Charles was "accelerated" by the Panorama programme.