Princess Margaret, Queen Mother and Queen Elizabeth II
Princess Margaret, Queen Mother, Queen Elizabeth II, Prince Harry, Prince Charles and other members of the royal family watch an honour guard on Aug. 4, 1997 in London. Getty Images/Adrian Dennis

Princess Margaret caused a sensation in 1978.

In Channel 5’s documentary “The Royal Family: Affairs and Infidelities,” it was revealed that the Queen’s sister was the first royal to go through a divorce after 400 years since Henry VIII made the same move to end his marriage with Catherine of Aragon in 1540.

“The divorce could be considered a landmark moment in royal history,” the narrator read. “Princess Margaret would be the first major royal to get divorced in over 400 years.”

Princess Margaret was known for being a “glamorous rebel” during her lifetime. Her split from her husband of 18 years, Anthony Armstrong-Jones, was shocking and only came after her affair with a younger man went public.

Queen Elizabeth II’s only sibling was 44 when she was romantically involved with then 27-year-old Roddy Llewellyn. The pair sent the press into a frenzy when they were photographed together on the island of Mustique in 1976. The pictures were fairly innocent by today’s standards, but it caused Princess Margaret’s shocking divorce two years after.

“He was highly unsuitable, so these photographs were fairly dramatic really,” royal biographer Anne Sebba explained.

According to Sebba, Princess Margaret was Queen Elizabeth II’s sister so Llewellyn’s presence had a huge impact to the royal family and their stability.

Ingrid Seward, editor of Majesty magazine, added that Princess Margaret’s divorce was “extremely shocking” because she was very close to Queen Elizabeth who is the head of the Church. Princess Margaret and Armstrong-Jones got married in 1960. He was the first commoner to marry a king’s daughter in over four centuries.

In related news, Princess Margaret and Princess Diana had a cold war. The Queen’s sister was mad when she learned about the late Princess of Wales interview where she said that her relationship with Prince Charles didn’t work because “there were three of us in this marriage.”

Princess Margaret found the People’s Princess’ comments “unacceptable,” so she never spoke with Princess Diana after the interview.

Meanwhile, Princess Diana reportedly used Princess Margaret’s front door when she snuck her lover into the palace. It was the only door without a CCTV camera because Princes Margaret insisted not to place one there as she was very intent on her privacy.