Oprah reveals she and Prince Harry have already had several 'secret meetings' for their new TV show

Oprah Winfrey has spoken about her new documentary series with Prince Harry.

During an appearance on CBS's This Morning, hosted by Oprah's best friend Gayle King, the TV doyenne was asked about her Royal collaboration.

"Oh, is that out now?" she said with mock surprise, after the news made worldwide headlines.

Oprah revealed there's already been several "secret meetings in London" and added Prince Harry has been really hands on.

"I've flown there with the crew, sitting in sessions talking about the directions we're going to take [with the series]. "

"Our hope is that it will have an impact to reduce the stigma and help people to know they're not alone, allowing people to speak up about it and identify it for themselves and their friends," she told the panel.

Appearing on the show to promote her new book, just hours after the announcement from the Palace, Oprah explained how their collaboration came about.

"I was actually having a conversation with him about 'what do you think are the most important issues facing the world right now?' and he said, 'there are two - climate change and mental wellness/mental fitness' and he said 'mental wellness', those were his words."

"As you know, he's spoken about his own issues and what he went through after his mother died and how being able to talk about it has benefited him. So, it's a passion of his... and at the end of the conversation I said 'Oh I'm going to be doing this thing with Apple, cause it's a big concern of mine too and I want to try and erase the stigma and I was telling him about this Apple platform and he said at the end of the conversation 'Oh if there's anything I can do to help...' and I go 'ahhh, as a matter of fact'," she trailed off with a laugh.

The Duke of Sussex formally announced the joint project on Wednesday - for which the pair are co-creators and will both serve as executive producers.

"I am incredibly proud to be working alongside Oprah on this vital series which we have been developing together for several months," Prince Harry said in a statement, also posted to Instagram.

"I truly believe that good mental health – mental fitness – is the key to powerful leadership, productive communities and a purpose-driven self.

"It is a huge responsibility to get this right as we bring you the facts, the science and the awareness of a subject that is so relevant during these times.

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"Our hope is that this series will be positive, enlightening and inclusive – sharing global stories of unparalleled human spirit fighting back from the darkest places, and the opportunity for us to understand ourselves and those around us better. "

The multi-part documentary series will air on Apple TV in 2020 and will focus on both mental illness and mental wellness.

Oprah Winfrey recently fronted the Apple TV announcement in San Jose, among a list of stars including Jennifer Aniston and Oprah Winfrey recently fronted the Apple TV announcement in San Jose, among a list of stars including Jennifer Aniston and.