Prince Charles never loved Princess Diana, he had confessed in a biography that was published in 1994.
That Princess Diana and Prince Charles' marriage was one fraught with unhappiness is known to most people. But, what is not known is if Charles ever loved Diana. Knowing that would bring perspective to his actions throughout their relationship. He caused her deep sadness during the many years they were together and even in the end, he made sure that she doesn't get the respect of being the mother of a future king.
By the time of Prince Harry's birth in 1984, Princess Diana had known that her husband didn't love her at all. The night Harry was born, she cried herself to sleep because of something Charles said to her.
As per Sun UK, former butler Paul Burrell, who worked with Diana for ten years until her death, revealed, "I could see the cracks in the marriage getting wider and wider. Diana confided in me that on the night Harry was born, she cried herself to sleep." "She said, 'I knew my marriage was over.'" Burrell also said that Charles had told Diana that his "duty" as a husband was over after Harry's birth.
"He’d provided the country with an 'heir and a spare', and could now resume his relationship with Miss Camilla Parker Bowles," said Burrell. And, Charles did resume the affair, which eventually led to his and Diana's divorce.
According to The Seattle Times, Charles said in an authorized biography in 1994 that he never loved Diana. Diana's friend had then said, "She is devastated. She can hardly believe what her husband has done to her. On the advice of her friends and presumably her lawyers, she is keeping her head down and saying nothing."
At the time, Buckingham Palace had said that Charles had no regrets about cooperating for the frank biography. He had revealed that he was in a nightmare marriage with a bored, bulimic, self-absorbed, and obsessively jealous young wife.
The future king had given author Jonathan Dimbleby access to diaries and letters that talked about the details of his marriage. It had described Prince Philip as a domineering father who forced Charles to marry Diana.
Prince Philip, Duke of Edinburgh, apparently made Charles marry her in 1981 as her reputation and that of the royal family was being "compromised" due to her visits to Balmoral castle. Charles' father told him to either marry her or leave her. Diana had been only 18 at the time while Charles was 30. "The prince interpreted his father's attitude as an ultimatum," the book, Prince Charles: A Biography, said. He married Diana in a "confused and anxious state of mind."
According to the New Yorker, he thought it was "the right thing for this Country and for my family."
After their wedding, Diana reportedly had "bouts of unhappiness" and would "sit hunched on a chair, her head on her knees, quite inconsolable. . . . Yet she scoured every tabloid newspaper for photographs of herself, as if hoping to discover her identity there," according to his biography, as per The Seattle Times. "Even the Falklands campaign (the British war with Argentina over the Falkland Islands) failed to arouse her curiosity. . . . Indeed, she seemed to resent the interest being shown in the Falklands rather than in her," the book claimed.
One time, Charles "watched her tears flow and, on one occasion, he had sat much of the day alone with her, (while she was) bowed in silence, apparently insensible to his presence." In another part of the book, it said that the prince wrote that he was in "total agony about the situation and I don't see how much longer one can go on trying to sweep it under the carpet and pretend nothing is wrong."
Charles acknowledged that he cheated on Diana but only after their marriage had failed. However, as he never loved her it is not sure at what point he considered his marriage a failure. He told Dimbleby that Camilla Parker-Bowles, who was then considered his mistress, was and would remain among his closest friends. He went on to marry her in 2005.
References:
https://archive.seattletimes.com/archive/?date=19941017&slug=1936490
https://www.newyorker.com/magazine/2017/04/10/where-prince-charles-went-wrong