For the 750 million people watching, the royal wedding appeared to be the perfect fairytale. However, the royal pair had their share of difficulties and later separated and divorced.

       A royal expert has laid bare Diana's fears on her wedding day and her discomfort when seeing Prince Charles' ex-girlfriend in the pews at St Paul's Cathedral.

       Princess Diana, 19 at the time, felt like a “lamb to the slaughter” on her wedding day in 1981.

       Speaking on the Channel 5 documentary Charles and Camilla: King and Queen in Waiting, former BBC correspondent and royal expert, Jennie Bond confirmed Lady Diana was not happy on her wedding day.

       “Diana told me much later in one of our private conversations that she had felt like a lamb to the slaughter as she walked up the aisle, which is very sad, but I think she knew that things weren’t quite right,” she said.

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       “When she saw Camilla in the congregation she was immediately uneasy about it.”

       Recordings which confirm the Princess of Wales' fears going into her marriage were given to journalist Andrew Morton.

       Young Diana said her wedding day was the “worst day of her life”.

       She also talked about how she “cried my heart out on my honeymoon”.

       Charles and Diana separated in 1992 and later got a divorce in 1996.

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       The Queen sent Princess Diana a letter, urging her and Charles to get a divorce, even though Diana did not want one.

       "I have consulted with the Archbishop of Canterbury and with the Prime Minister and, of course, with Charles, and we have decided that the best course for you is divorce,” the Queen wrote in 1995, following Diana's Panorama interview.

       In 1993, an intimate phone call was leaked between Charles and Camilla, which led to a large scandal.

       Camilla divorced her then husband Andrew Parker Bowles in 1995.

       Following Diana's tragic death in 1997, Charles and Camilla made their relationship public and married in 2005.