Oprah Winfrey "cannot out-happy" Gayle King

She told 'Moments That Make Us': "The reason why I think our friendship has worked is because Gayle is happier, not happy, but happier for me for any kind of success or victory or challenge I get through than I am for myself. And I feel as happy as she does - I can't be happier than, cannot surpass Gayle. You cannot out-happy her. I am equally as happy for her."

Gayle believes they've both benefitted from being open and honest with each other.

She explained: "In Oprah's life, everybody is always very flattering and is always very agreeable with things that she says. And sometimes I'll just go, 'That's just not true. Your hair does not look good.'"

Earlier this year, Oprah revealed that she turns to Gayle for "real therapy".

The veteran TV star has often turned to her friend for help and support, rather than a professional therapist.

Oprah told PEOPLE: "I've never been to a therapist because I had so many on the show, but my real therapy came from downloading whatever was happening in the day with Gayle every night."

Oprah and Gayle also supported each other throughout the early years of their careers.

The TV icon shared: "There wasn't a day that we missed being on some kind of phone call talking about what had happened in our days."

Oprah is now hugely grateful for Gayle's support.

She said: "I've had one of the best friendships anybody could have. And you can only do that when somebody cares as much about your success, your sadnesses, your triumphs as you do."