King Charles, who had a troubled marriage with ex-wife Princess, deep down held some sincere feelings for her.

In newly-revealed letters by Daily Mail, written by the monarch, showcased a rare side of the monarch towards Diana, in which he describes the pain he felt following her fatal accident.

The three-page handwritten letter was dated December 8, 1997, with a Highgrove House letterhead, and signed “Charles.” The letter was reportedly delivered “by hand” to the recipient, per the then-Prince’s instructions.

Diana died in a fatal car accident in Paris on August 31, 1997. She was 36 years old.

Penned just four months after Diana’s death, Charles dubbed his grief as “unbearable emptiness” which he felt in the wake of Diana’s death, as he consoled his friend Peter on the passing of “dear Liz.”

He empathised with Peter’s “agony” and admitted that he “longed to wave a magic wand to transform the situation” and rid himself of the “bewilderment and confusion that accompanies the removal of someone so young from the world.”

Charles also mentions in the letter, “My heart bleeds for you as I can imagine so well the utter agony and despair you must have gone through during all these heart-rendering months that you have known about Liz’s illness.”

The rare admission of Charles' feelings for Diana appear unusual as the couple went through a messy split, given that the royal was still in love with his former girlfriend and now-wife, Camilla.

Diana alleged that Charles continued to have relations with Camilla while he was still married to her.