Britains King Charles III fondly referred to Meghan Markle as Tungsten, according to a new book.

The moniker paid tribute to the Duchess of Sussexs toughness and resilience, Vanity Fair royal editor Katie Nicholl wrote in The New Royals out this week.

ET Online shared excerpts from the book on Tuesday.

The then-Prince Charles complimentary likening of Markle to the rare, metallic element which is one of the toughest items found in nature came before her 2018 wedding to his son Prince Harry .