The Duchess of Edinburgh was among the royals to join the King and Queen at a special Windsor Castle reception on Tuesday evening.
Charles, 74, and Camilla, 76, watched moving performances from Shakespeare's plays as they marked the Bard's contribution to the life and culture of the nation.
Their Majesties were also accompanied by the Duke and Duchess of Gloucester and a host of the country's leading actors, including Dame Judi Dench and Helena Bonham Carter.
Celebrations are being staged this year to mark the 400th anniversary of the first printed edition of Shakespeare's collection of plays, commonly referred to by modern scholars as the First Folio.
It was published in 1623, seven years after Shakespeare's death and is a collection of 36 of the Bard's works, compiled by his fellow friends and actors, John Heminges and Henry Condell.
A copy of the First Folio, which is held in the Royal Library at Windsor Castle, was on display during the reception, with the King and Queen seen looking at the rare manuscript after the performance, as seen in the clip below...
Queen Camilla, who celebrated her birthday on Monday, looked elegant in a cobalt blue dress with ruffled sleeves, while sister-in-law Sophie was dressed in a navy dress with a gold patterned motif.
Taking to the stage to read extracts from Macbeth, Julius Caesar, As You Like It, Twelfth Night, Antony And Cleopatra and The Tempest was a small ensemble of actors, including Ray Fearon, a former Coronation Street star, Lucy Phelps, Sir Simon Russell Beale and Dame Harriet Walter.
After the performance, Lucy Phelps joked the issue was the "acting royalty" in the first few rows, and not Charles and Camilla.
She said: "I thought it was going to be a bit like Strictly (Come Dancing) with Judi Dench holding up a card with a number seven on it. Just with all those actors in the room with us who have played those parts, that was the thing."
As Prince of Wales, Charles became President of the Royal Shakespeare Company in 1991 and is known to take a keen interest in Shakespeare, having performed in plays whilst at university.
In 2016, Charles visited New Place - Shakespeare's last home in Stratford-upon-Avon and also joined renowned theatre actors on stage at Stratford to perform Hamlet as part of Shakespeare Live! from the RSC.