The love triangle between Princess Diana, Prince Charles and Camilla Parker Bowles is something which people can never get tired of talking about. And now, in a shocking revelation, it has been found that the late royal may have had an idea about Prince Charles' love for Camilla when he proposed marriage to Diana, reports Express UK.

In a television documentary titled 'Diana: In Her Own Words,' video footage shows Diana discussing various parts of her interesting life, including her marriage to Prince Charles, the Duke of Cornwall. The documentary was broadcast last year on Channel 4 on August 6, to mark the 20th anniversary of Diana's death.

The recorded conversations reportedly took place between Diana and her voice coach in 1992 and 1993. 16 minutes into the documentary, Diana made the revelation that she knew her husband-to-be was secretly in love with his current wife Camilla (who would late become Duchess of Cornwall), whom he married in April 2005.

Diana said: “Charles rang me up from Klosters (Switzerland) saying: 'I’ve got something to ask you.' Instinct in a female - you knew what was coming. I sat up all night with my girls, saying: 'What do I do? What do I say?' By that time I had realized there was someone else around.”

The People's Princess went on to add that she realized the person Charles was talking about was, in fact, Camilla when she spent a lot of time with her family and started to observe Camilla's everyday behavior with Charles. 

She said: “I had been staying at Bolehyde with the Parker-Bowleses an awful lot. I couldn’t understand why Camilla kept saying to me: 'Don’t do this. Don’t do that.' She knew so much about what he was doing privately. Eventually, I worked it all out.”

When Prince Charles decided to ask Diana for her hand in marriage, the Princess admitted she thought it was a “joke” at first. However, she accepted his proposal after giving a lot of thought to it, eventually believing that Charles indeed must love her genuinely and deeply.

Diana said: “He sat me down and he said: 'Will you marry me?,' and I laughed. I remember thinking: 'This is a joke,' so I said: 'Yeah, ok,' and he was deadly serious."

After the late princess accepted Charles' proposal, when Charles warned her that she might become the future Queen of England, Diana shrugged off the thought, assuming that being Queen would simply mean that she would have a slightly "tougher role."

“He said: 'You do realize that one day you will be Queen.' A voice said to me inside: 'You won’t be Queen, but you’ll have a tough role.' So I said: “I love you so much! I love you so much!, and he said: 'Whatever love means' So I thought that was great! I thought he meant that.”

Diana added: “In my immaturity, which was enormous, I thought he was very much in love with me, which he was. He sort of had the besotted look about him looking back at it, but it wasn’t the genuine sort. You know, who is this girl who is so different? But he couldn’t understand it because his immaturity is quite good in that department.”

When the documentary first aired, it gave Channel 4 its largest overnight ratings for a year, watched by an average audience of 3.5 million, peaking at 4.1 million viewers.