Lionel Richie Reacts to King Charles and Queen Camilla's Surprise Cameo on 'American Idol' (Exclusive)

King Charles III and Queen Camilla surprised 'American Idol' audiences during the May 7 episode.

Lionel Richie is looking back on his time in London fondly! 

Earlier this month, the "All Night Long" singer performed at King Charles III and Queen Camilla's royal coronation, and to return the favor, the newly crowned monarchs made a surprise cameo on American Idol

Speaking with ET's Denny Directo after Sunday's Disney Night episode of Idol, Richie gushed over how "gracious" Charles and Camilla are. The singer then revealed he was the one who asked the royals if they were interested in doing an impromptu cameo on the show. 

Explaining how the conversation with King Charles transpired, Richie revealed, "When I said, 'Would you like to join me on the show?' Immediately, he said, 'Yes, I would.'" 

"It was fabulous," Richie noted. 

Charles and Camilla's appearance on the long-running singing competition series came at the start of the May 7 show and just hours after both Richie and fellow Idol judge Katy Perry performed at the coronation concert at Windsor Castle.

Perry and Richie, who were broadcasting live from the castle for their address, were met by the new monarchs who jokingly asked how long they were planning to use the room for.

Jokes aside, both Charles and Camilla thanked the singers for their "brilliant" performances and invited Perry and Richie to the concert's after-party as soon as they wrapped up their Idol duties.

The coronation concert proved to be an exciting one for the judges, with Richie getting Charles up on his feet with his hits, "Easy (Like Sunday Morning)" and "All Night Long," and Perry moving Princess Charlotte to sing along to "Roar," before having the entire audience feeling like a "Firework."

Ahead of the special concert, ET spoke with Richie, who called being invited to perform for the king, "An honor."

"I mean, first of all, when you've been in the business a long time, and, of course, when you get an invitation like this, the answer is absolutely," Richie told ET. "We've been friends a long time, I've known him a long time, but to be asked is the whole thing."