King Charles and Princess Diana got separated from each other in 1992    

King Charles penned a riveting letter to Princess Diana the night before their wedding.

The couple, who tied the knot in 1981, marked one of the most popular royal family weddings.

While the matrimonial was arranged by their parents, the King ensured to send his future wife a special note ahead of the big day, noting his love for her.

Royal author Penny Junor reveals: "The night before the wedding, which Diana spent at Clarence House with her sister Jane, he sent her a note, along with a signet ring that bore the Prince of Wales feathers.”

The King in his letter wrote, 'I'm so proud of you and when you come up I'll be there at the altar for you tomorrow. Just look 'em in the eye and knock 'em dead.’”

King Charles and Diana parted ways in 1992 after an unhappy marriage and two children. His Majesty married Queen Camilla in 2005.