King Charles smiles as he fulfils his promise to Camilla

King Charles III amazed royal fans with his sweet gesture to Queen Camilla after fulfilling his decades-old promise to his second wife on Saturday.

The 74-year-old monarch, already wearing the St Edward’s Crown, watched as Camilla, 75, performed the solemn elements of her part of the Westminster Abbey ceremony.

The 74-year-old smiled as he looked at her during the coronation ceremony on May 6, leaving royal fans guessing about his gesture to the Queen.

As the Queen curtseyed to her husband, the King gave a small smile and a blink, taking it all in. The Queen smiled back at him, visibly relaxing as she made her way to the Chairs of Estate.

Reacting to the monarch's gesture, one royal fan twitted: "Wow! King Charles' smile reveals he has fulfilled his promise to Camilla."

Another wrote: "He did..."  While others appreciated the moment and prayed for the couple.

Camilla, who wore the heavy Queen Mary’s Crown, was seen adjusting her hair. While, the King could take in the full meaning of the moment.

The crowning moment appeared to be the the culmination of a long journey for the couple, who married 16 years ago in very different circumstances.

Camilla's journey from romantic involvement, to mistress and finally wife of the King Charles has been played out over more than five decades, and ended with her formally becoming the nation’s Queen.