Diana reveals she caught Prince Charles sitting on the loo talking dirty to Camilla on the phone and says she would do 'everything possible' to stop him becoming king in newly unearthed interview

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Princess Diana caught Prince Charles sitting on the toilet as he made private phone calls to Camilla Parker-Bowles, new tapes claim.

The late Princess of Wales described her husband's mistress as the 'raunchier' of the two after listening in on their explicit conversations and spoke of a desire to stop Charles becoming King.

Her intimate thoughts emerged in 12 hours of unseen footage, filmed by a handpicked cinematographer as she offloaded years of royal secrets in the months before her death.

The new tapes are separate to recordings she made five years earlier with voice coach Peter Settelen which are due to be broadcast tonight for the first time on Channel 4.

Princess Diana speaks about how she caught Prince Charles speaking to Camilla on the phone in tapes due to air for the first time tonight 

The late Princes of Wales described her husband's mistress as the 'raunchier' of the two after listening in on the calls

Diana described her sex life with Prince Charles (both pictured) as 'very odd' during a taped session with voice coach Peter Settelen

Mr Settelen began recording interviews with Diana in September 1992, three months before her official split with Prince Charles. They continued to meet and record until December 1993. 

But in new footage which has come to light today, a cameraman has spoke anonymously to The Sun about the tapes recorded of the royal in 1997 before she died.

The newspaper reports the cinematographer was working for the BBC when he was summoned to Kensington Palace late one night.

He was paid £5,000 for his time and kept a personal diary of his meetings with Diana, noting how she was determined not to let Charles become King.  

Diana: In Her Own Words is centred around the tapes recorded by her speech coach and ex-Coronation Street actor Peter Settelen

The lensman wrote: 'Diana caught Charles and Camilla de flagrante after listening in to his phone calls.

'She described how she came to listen to their phone calls. In one, Charles was sitting on the toilet seat when she caught him.'

The topic of conversation was described as 'phone sex' where it was claimed Camilla was the more saucier of what happened. 

Diana also spoke about her desire to stop Charles from becoming King, instead wanting her eldest son William to take up the position.

The camera operative put in his diary: 'She makes it clear that she would do everything possible to make sure Charles never became King.

'She wanted William to succeed to the throne when the Queen died. Diana clearly saw her role as the power behind William.

'She had this somewhat romantic idea of being a king-maker, the mother behind the monarch.'

During the explosive interviews with Mr Settelen, Diana discusses Charles' relationship with Camilla Parker Bowles. Pictured, the pair together in 2000

The lensman who is still alive and understood to be living in America described the moment he arrived at Kensington Palace and was waved through by police.

He said he had to buy two burner phones amid fears Mi5 would hack their conversations.

These fresh claims come just hours ahead of a worldwide premiere of a never-seen-before interview with the Princess. 

Mr Settelen fought a bitter legal battle against Diana's family for ownership of his tapes, which were finally handed back to him in September this year. 

They disappeared from Diana's apartment at Kensington Palace after her death in 1997 but were discovered four years ago in the loft of her former butler, Paul Burrell. 

In an interview to accompany the tapes, Mr Settelen says Diana came across as a 'frightened woman' who was 'shellshocked by a bad marriage'.  

The cameraman, who wishes to remain anonymous, claims he worked for the BBC and was summoned to Kensington Palace late one night.

The Sun reports how the cinematographer kept a diary of the sessions in which

Tonight the controversial recordings, documenting the collapse of Diana's marriage to Charles, will be aired on Channel 4.  

Diana revealed that her and Charles went from having sex 'once every three weeks' to it fizzling out all together. Left, on their honeymoon in 1981 and right, at a polo match in 1985

The tapes went missing and Mr Settelen became locked in a copyright battle with Diana's brother, following her death, for the rights to broadcast them.

He eventually won and was backed by NBC who wanted to broadcast the footage.  

Settelen was hired by the princess to build her confidence in public speaking but in the process recorded her no-holds-barred confessions about the royals. 

This isn't the first time details about Prince Charles' private contact with his now-wife have come to the fore. 

In 1992, a highly personal transcript of the 'Camillagate' call was made public.   

It caused huge embarrassment to the Royal Family as it included details of how the prince had told his lover that he wanted to be her 'tampon'.

Minutes from a security meeting describing the inquiry into the Camillagate scandal were read to the London hearing into the death of Princess Diana and her lover Dodi Fayed in 2008.

Lord Fellowes, who was then the Queen's private secretary, told the gathering in April 1993: 'Evidence had been found that the fixed telephone lines had been tampered with. 

'It was almost certain that this was the location where the Prince of Wales had been staying on the night of the alleged conversation between him and Mrs Parker Bowles.' The location was not named, but it is thought to be Eaton Hall in Cheshire, home of Charles's great friend, the Duke of Westminster.

The prince is thought to have enjoyed clandestine meetings with Camilla at the house.

The inquest heard that Charles made the call to Camilla, who was at her home in Wiltshire, on a mobile phone, not a landline.

But the minutes from the meeting showed that Sir Robin Butler, the then Cabinet Secretary, was so concerned about the tampering that he asked whether all royal premises should be checked for listening devices.

The latest revelations emerged as Sir John Adye, the head of GCHQ from 1989 to 1996, gave evidence.

He dismissed claims that the service was bugging the royals and said it was 'nonsense' to suggest that they were behind the Camillagate and Squidgygate tapes.

Under the law GCHQ would have needed to get the Foreign Secretary to sign off such a phone tap, which the agency had not sought, he said.

Ian Burnett QC, for the coroner, said at the time: 'And intercepting the Royal Family is simply not within the scope of the intelligence the government was seeking?'

Sir John replied: 'Indeed, it was not.'