In a recently unearthed clip from 1997, Allan Starkie, author of ‘Fergie, Her Secret Life’, said he learned of the women’s pact during a train journey with Sarah’s lover John Bryan, an oil tycoon.
“Early in 1992, I went in a trip to Dartmoor with John Bryan, this is very early in to his involvement with the duchess and on the way back on the train he told me that Princess Diana and the duchess had formed a divorce pact together some time before, where they were going to divorce their respective spouses simultaneously.
“But the palace convinced them that it was going to be too destructive for that and it would be staged.”
However, news of Fergie and Prince Andrew’s marital woes were leaked to the press in 1992 before the pair had time to stage a separation.
And instead of leaving Prince Charles despite having been unhappy for years, Diana decided to stay with her husband to avoid public ridicule.
Judy Wade, writer and royal journalist, said Sarah’s exit from the Royal Family was a “rehearsal” for Princess Diana.
She said: “A lot of people, including myself at one time, did believe perhaps somebody sympathetic to Diana had leaked the story of Fergie’s wish to leave Andrew because they thought that it would help Diana find out what would happen to Sarah if she left, it would be a kind of rehearsal for Diana.
“It certainly looked that it was certainly beneficial for Diana and she quickly changed her mind and put off her separation for some time.
“At one stage Sarah and Diana were determined to leave together but that didn’t happen and obviously Diana saw that Fergie was quickly victimised by the palace.”