Sarah Ferguson kept Andrew blindsided of her darker secrets

Sarah Ferguson’s infidelity towards Andrew is laid bare in new book.

The former Duke and Duchess of Sussex called it quits back in 1990s after scandalous affairs.

Writing in his memoir 'Fergie - Her Secret Life,' ex pal Dr Allan Starkie reveals how Sarah cheated on Andrew with lover John Bryan back in the days.

According to the Daily Mail: "When John Bryan came to stay at Sunninghill, he and Sarah would indulge in s** acts in Andrew's study after the prince had gone to bed. She didn't care. 'Vulgar, vulgar, vulgar,' stormed the Queen's former private secretary, Lord Charteris."

Sarah was later insulted by Princess Anne, Andrew’s elder sister.

The author reveals: "There was not one voice raised against Anne. Andrew's anger melted into sadness, and he buried himself in the special reports compiled for the Queen, which she did not hesitate to let him read."

Over confrontation with Queen Elizabeth II, the author adds: "She acted in the strangest way. You would have thought she was the person wronged, as if she had every right to go on holiday with another man, kiss and cuddle him, and the only person who had behaved wrongly were the photographer and the editors of the newspapers who had published the pictures."