Meghan Markle, 38, and Prince Harry, 35, stepped down as senior members of the Royal Family at the end of March after announcing plans to become financially independent and split their time between America and UK in January.
The Duke and Duchess of Sussex have been stopped from working under their royal titles by the Queen. But Princess Anne, 61, has warned the couple against their progressive stanch to the monarchy.
Princess Anne has previously said: "I don't think this younger generation probably understands what I was doing in the past and it's often true, isn't it?
"You don't necessarily look at the previous generation and say, 'Oh you did that?' or 'You were there?'
"Nowadays, they're much more looking for, 'Oh let's do it a new way.'
"And I'm already at that stage, 'Please do not reinvent that particular wheel.
"We've been there, done that.
"Some of these things don't work.
"You may need to go back to basics.'"
Her comments come as Royal expert Angela Mollard has warned the couple from doing so and said the interview would be a car crash.
Comparing it to Princess Diana's interview after divorcing Prince Charles, she said Meghan would be hammered because she doesn't have the same affection from the public.
Speaking on New Idea's ROYALS podcast, Ms Mollard said: "It's been touted they would be paid a $1million which isn't a lot really.
"I know it does seem a lot but for an interview of that magnitude.
"If they were to sit down with Oprah because Meghan is friends with Oprah and speak in any detail about the Royal Family and it would have to have some elements of that. It would be car crash Prince Andrew-style part two."