Lionel Richie is set to perform at King Charles' coronation concert on Sunday, but his connection to the royal family goes back decades.

In 2015, Richie attended a charity fundraising event for Jewish Care which also welcomed Prince William. During a speech, the musician shared that he had the privilege of meeting William's mother, Princess Diana, about 10 years before her death in 1997.

"Many years ago I had the pleasure of meeting Princess Diana and tonight we have Prince William here," Richie said in 2015, per E! News. 

KING CHARLES' CORONATION CONCERT: KATY PERRY AND LIONEL RICHIE WILL PERFORM

"I must tell you it is a pleasure to be with all of you but especially this gentleman, because his mother came to me...and she said, 'My favorite song is 'Hello.'' So I thought, tonight the dedication is to you, my friend."

William thanked Richie for his kind words and "giving your time to entertain us."

"I imagine the crowd here will be rowdier that what you'll have at Glastonbury," William joked.

Richie and Diana first crossed paths during his concert in London in 1986. At the time, Richie performed his 1984 hit, "Hello," which he shared was Diana's favorite song. The singer and his then-wife, Brenda Harvey, also gifted the princess two leather jackets for her sons: William and Harry. The boys were 4 and 2 at the time.

For Charles' coronation concert on Sunday, the "All Night Long" singer will be joined by fellow "American Idol" judge Katy Perry and Andrea Bocelli, Take That, Sir Bryn Terfel, Freya Ridings and Alexis Ffrench.

In an interview with E! News at the Breakthrough Prize ceremony last month, Richie shared his own tips for when it comes to navigating royal protocol ahead of his trip across the pond.

"There's always something where I go, 'Oh, I didn't know that,'" he told the outlet. "Be prepared, just be sure to just say sir and ma'am—forget everything else. Just remember sir and ma'am, and you kind of walk your way through."

Richie explained that Charles personally requested a specific song for him to perform at the coronation concert.

"And the answer is yes, I will do it," he said. "We will not reveal because it's completely enveloped in secrecy. So, all I can tell you is I'm very happy to be there."

Richie could not be happier for Charles on his big day. The king immediately ascended the throne in September after his mother, Queen Elizabeth II, died at age 96.

"I'm very happy for him," Richie said. "He's kind of waited in that second position for a very long time. And I think what we're gonna get now is the new version of the royal family. I'm looking forward to see what he's going to bring to the table, and I can tell you right now, he's gonna change it up a little bit."

The "Hello" singer also spoke with Entertainment Tonight at the event, noting his longtime collaborations with the king.

"We've been friends a long time, I've known him a long time, but to be asked is the whole thing," Richie said. The singer has worked for many years as the founding Global Ambassador for the Prince’s Trust, a charity Charles began when he was the Prince of Wales dedicated to helping young people "get into jobs, education and training," per its website. 

Richie also teased the preparation involved in the show, saying, "There's more secrecy than you've ever imagined in your life."

"I know what I'm going to do but when you ask, 'What is everyone else going to do?' Nothing. 'Who is everybody else?' 'Hmmm.' 'OK, well, what's the production going to be like?' [No response]," he explained. "So we won't really know until we get there for the rehearsal to find out exactly how big."

KATY PERRY HOPES TO BRING 'LIGHT AND LOVE' TO KING CHARLES’ CORONATION CONCERT

"And, by the way, I'm going to use that word 'huge.' Not just big, [it's going to be] off the charts," Richie added.

Meanwhile, Perry has a special relationship with the king herself.

In 2020, at the Banqueting House in London, Charles announced the "Firework" singer as an ambassador of the British Asian Trust’s Children’s Protection Fund for India.

The pair first met in India in November 2019, People magazine reported. Perry was in Mumbai as a UNICEF Goodwill Ambassador at the time. 

Last week, Perry explained that she hopes to bring "light and love" to Charles coronation.

"It's natural because it's a foundation that helps in child trafficking which is massive and horrible," Perry explained in an interview to Access Hollywood. "I'm also an ambassador for UNICEF, so both of those things really are my core values and as a mother, I know first hand what's most important — which are these innocent children."

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She continued, "I'm going there to represent myself as an ambassador and just to bring the light and the love. That's all I ever want to bring."

The coronation concert is set for May 7, the day after Charles is officially crowned king alongside Camilla, who will be crowned queen.