The late Princess Diana would have been 'broken-hearted' about Prince William and Prince Harry's feud, according to a royal expert. 

Richard Kay, editor-at-large for the Daily Mail, told the Mail+'s weekly talk show that if Diana was still alive, the 'tussle' between her two sons would not exist. 

Tensions have been rising between the Princes ever since the Duke and Duchess of Sussex quit their roles as senior working members of the Royal Family in January 2020, before moving to America in June of that year at the height of the Covid-19 pandemic. 

Kay, who was a very good friend of Princess Diana and would speak with her up to six times a day, said Harry and William have been fighting over her 'legacy'. 

He told Palace Confidential: '[They've] been tussling over Diana's legacy, they've been pulling apart Diana's legacy, [and picking] which part suits them best. I think it's a great tragedy. 

Princess Diana is pictured with both of her sons, Prince William and Prince Harry, in London in 1995

Princess Diana is pictured with both of her sons, Prince William and Prince Harry, in London in 1995

'What I knew about Diana was, first and above all, was her love for her sons, that was clear to the whole world, she loved those boys. I think she would've been broken-hearted.

'The big question is, would it have still happened had Diana still been with us? My own view is that it probably wouldn't have because she would've remained the pivotal figure in both their lives and prevented the fallout from happening.'

Harry and William have endured a famously frosty relationship in recent years - with the Prince of Wales not seeing his younger brother during his whirlwind trip to the UK in May.

In his memoir, Spare, Harry went as far to call William his 'archnemesis' and said the duo have always 'competed' and detailed alleged physical altercations between the pair.

It is believed the trigger that caused the rift to first develop between William and Harry was when the then Duke of Cambridge advised his younger sibling to 'take things slow' when he first began dating Meghan Markle in 2017.

Relations soured more after Megxit and a source previously told People that the brothers' relationship is 'forever changed' and they 'won't get back to the way they were'. 'Harry is looking straight ahead at his future with his family,' they added.

Meanwhile, Kay said he believed Princess Diana - who died in a car crash in Paris in 1997 - would have been 'proud' of William and Kate for stepping into their places as Prince and Princess of Wales.

'I think she would've been proud of William and Catherine and what a stylish edition they've made and how they've seamlessly stepped into hers and Charles' shoes with a young family,' he added.

Tensions have been rising between Prince Harry and Prince William (pictured in 2021) ever since the Duke and Duchess of Sussex quit their roles as senior working members of the Royal Family in January 2020

Tensions have been rising between Prince Harry and Prince William (pictured in 2021) ever since the Duke and Duchess of Sussex quit their roles as senior working members of the Royal Family in January 2020

Richard Kay, editor-at-large for the Daily Mail, (pictured) told the Mail+'s weekly talk show that if Diana was still alive, the 'tussle' between her two sons would not exist

Richard Kay, editor-at-large for the Daily Mail, (pictured) told the Mail+'s weekly talk show that if Diana was still alive, the 'tussle' between her two sons would not exist

But the royal expert also said that Diana would have been 'hugely jealous' of the fact that Prince Harry was able to 'break away' from The Firm.

'You've got to remember, Diana was a radical, she was very unhappy, she was trapped within the royal system, she did try and break away, she couldn't quite before her death,' Kay said. 

'I think she would've been fiercely proud of the fact that Harry has chosen a life outside of the royal circle.'

Kay and host Jo Elvin also spoke about Harry's controversial acceptance of the Pat Tillman Award last month. 

He was an iconic NFL player who gave up his lucrative career to enlist in the army in the wake of 9/11 before his death in Afghanistan in 2004.

Tillman's own mother Mary revealed to DailyMail.com that she was 'shocked' that the ESPYs would 'select such a controversial and divisive individual to receive the award', adding that she was not consulted over the decision.

'There are recipients that are far more fitting. There are individuals working in the veteran community that are doing tremendous things to assist veterans,' she said.

'These individuals do not have the money, resources, connections or privilege that Prince Harry has. I feel that those types of individuals should be recognised.'

Princess Diana is pictured with her sons Prince William (left) and Prince Harry (right) during the summer holidays in Majorca in 1988

Princess Diana is pictured with her sons Prince William (left) and Prince Harry (right) during the summer holidays in Majorca in 1988

During his speech, Prince Harry said: '[Mary's] advocacy for Pat’s legacy is deeply personal and one that I respect.  The bond between a mother and son is eternal and transcends even the greatest losses.'

Kay said the Duke of Sussex was speaking about his relationship with his mother and the bond they had.

'It was clearly a reference to Princess Diana and his losing her at such a young age,' he said. 

'I think it was also a subtle way of him reaching out to Pat Tillman's mother who publicly expressed a strong view that Prince Harry was not the right person to be accepting the award.

'I think he was trying to amend bridges in the way he did it, but a lot of people were not impressed.'