Princess Diana made no secret of how isolated she felt after marrying into Britain’s royal family.

But she still tried to forge connections with her in-laws and sought out the late Queen Elizabeth II in her darkest moments, a new book claims.

According to a new royal biography, the late Princess of Wales would make unannounced visits to see her mother-in-law as the cracks in her marriage to King Charles III — then Prince Charles — deepened. And those emotional meetings were often filled with Diana’s tears.

Royal photographer and author Ian Lloyd shared the details in The Queen: 70 Chapters in the Life of Queen Elizabeth II, which was published in April to mark what would have been the late monarch’s 100th birthday.

One anecdote Lloyd shared, as reported by Marie Claire, revealed Diana’s sought help from the queen during the most painful years of her marriage.

“By the mid-1980s, Charles had resumed his relationship with Camilla Parker Bowles” — now Queen Camilla — “and Diana had embarked on an affair with former cavalry officer James Hewitt,” Lloyd wrote. “Although she professed being ‘terrified’ of her mother-in-law, Diana took to calling on the queen unannounced to pour out her heart to her.”

Lloyd added that Diana’s distress was sometimes visible before the meetings even began.

“Sometimes, the queen’s schedule meant the princess had to wait. One footman later reported to the queen, ‘The princess cried three times in a half hour while waiting to see you.'”

Elizabeth allegedly quipped back, “I had her for half an hour and she cried nonstop.”

Very different women

King Charles III married Princess Diana in 1981 in a fairy tale wedding at St. Paul’s Cathedral in London when he was 32 and she was 20. Their separation was announced 11 years later. By: ZUMAPRESS.com / MEGA

Despite Diana’s repeated attempts to confide in the queen, the biography suggests the two were never natural allies.

The queen and her late husband, Prince Philip, welcomed Diana into the family “in their own, no-nonsense way,” the royal biographer explained. “Elizabeth, however, struggled to find much in common with the new Princess of Wales and admitted she couldn’t understand her personality.”

It was a mismatch from the start — Diana was young, emotional and increasingly overwhelmed by royal life and Charles’ behavior, while Elizabeth was famously restrained, practical and deeply committed to the institution above all else.

As Charles drifted back toward Camilla and Diana became more miserable, that personality clash only added to Di’s feeling that she was navigating the monarchy alone.

Yet the fact that she kept showing up at the queen’s door seemingly meant she believed her mother-in-law was one of the few people in the family who could either comfort her — or help her change her circumstances.

Breaking point

By the early 1990s, the private heartbreak Diana shared in those meetings with the monarch had become a very public royal disaster.

British Prime Minister John Major announced Charles and Diana’s formal separation to the House of Commons in December 1992.

But things only deteriorated further after both Charles and Diana publicly admitted they had been unfaithful — him in a 1994 TV interview for the documentary Charles: The Private Man, the Public Role with journalist Jonathan Dimbleby, her in an infamous 1995 BBC Panorama interview with journalist Martin Bashir.

It proved to be the final straw for Elizabeth.

In December 1995 — after 14 years of marriage and with no hope of reconciliation — Buckingham Palace confirmed that the queen had written separate letters to Charles and Diana ordering them to divorce.

The divorce was finalized in August 1996 — just one year before Diana died at 36 following a Paris car crash, leaving sons Prince William and Prince Harry behind.