In a recent interview with BBC 1 Radio's Breakfast with Greg James, the 22-year-old singer, who recently visited Kensington Palace with the radio DJ, cautioned James, "Don't tell anybody what my mother and I did."
James didn't heed the warning, though, instead recalling, "We were at Kensington Palace... we were about to meet [Prince] William and Kate [Middleton] and I said, '[You] gotta steal something. Steal something... steal that pencil.'"
"And I was like, 'You triple doggy dare me?'" Cabello said.
"I did," James confirmed. "I triple doggy dared you."
"And you can't not do a triple doggy dare. If there's anything I've learned in my life, it's that," Cabello quipped in response, before confessing, "I did it."
To Cabello's recollection, James then told a palace employee what she'd done.
"You were like, 'She stole a pencil!' And I was like, 'Oh, my God,'" Cabello said. "And I put it in my mom's purse and my mom was like, 'No. We have to give it back. We have to give back the pencil.' And I was like, 'No. He triple doggy dared me. I have to take the pencil.' So I still have it."
"I'm sorry William and I'm sorry Kate," Cabello said to the Duke and Duchess of Cambridge. "... I honestly couldn't sleep last night. I had to get it off my chest."
The royals appear to have taken the theft good-naturedly, hilariously replying to a tweet with the eyes emoji.