The Princess told Women’s Weekly in Australia that the Queen had an “extraordinary perspective” on current affairs, valuing history while supporting the many different leaders she had worked with in their own right.

“It’s a very difficult thing to put your finger on,” she said of her mother’s legacy. “I doubt if there’s a single description that would fit the bill.

“There is an element of constancy here in terms of attitude to service and recognition of service, the values that individuals bring… I think she’s been able to support that and bring those people to the fore in a way that is so important.”

Of her late father, the Duke of Edinburgh, the Princess described his “unwavering support” for the Queen in the face of a tough start to royal life.

“I’m sure it wasn’t very easy to begin with because there was no such thing as a role then. He had to invent that one,” she said.

“I think he also understood the things he was better staying out of – although it was quite difficult in the early days – but there were also distinct areas where he could help and did.

“His input and perspective and the fact that his travels took him to a slightly different area of the country and internationally could have a real impact. I think he learned how to distinguish when those moments were.”

The Princess took part in a three-day tour of Australia to mark the Platinum Jubilee, paired with a short trip to Papua New Guinea. She first visited in 1970, when she undertook her first walkabout.