In a recently uncovered interview with Australian outlet 9Honey, the late Princess of Wales revealed she had made the secret trip before she became a widely recognised figure. Royal author Juliet Rieden recalled the secret visit made in February 1981 during a special edition of Talking Honey.

Ms Rieden said: “She came for a three-week holiday to stay with her mum in Yass and it was just a week after Prince Charles had proposed to her.

“She had said yes but it hadn’t been announced to the world.

“[Diana] had this really big secret that she was keeping, and was hiding away in Australia and pretty much came in under the radar.”

Ms Rieden said the Princess of Wales made the visit to the small town in New South Wales to ponder her future.

The trip came within the same month that the Royal Family officially announced the engagement.

However, in Andrew Morton’s book ‘Diana in Her Own Words’, the princess acknowledged that the trip was a “complete disaster” and looking back might have been a prelude to the eventual divorce.

She said: “I then went away two days later to Australia for three weeks to sort of settle down and to organize lists and things with my mother.

“That was a complete disaster because I pined for him [Charles] but he never rang me up.

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“I was asked to get her into the airport and onto the aircraft without going through the front door,” said Mr Wild.

He added that he had no idea who the mystery passenger was and initially believed it might have been a political defector.

Within a week of arriving back in the UK the engagement to Charles was announced.