The King delighted the audience at a production of Shakespeare's The Tempest by taking a seat near members of the public to watch the play.
As he arrived at the Royal Shakespeare Theatre (RSC) in Stratford-upon-Avon in Warwickshire on Friday night, Charles was greeted with cheers and waved to the crowd.
The RSC's co-artistic directors Daniel Evans and Tamara Harvey, and Lord Lieutenant of Warwickshire, Tim Cox, greeted the King on his arrival.
The King took a seat near the back of the theatre, between Mr Evans and Ms Harvey, for the sold-out production of Shakespeare's tragicomedy, which tells the story of two feuding royal brothers.
Sir Kenneth Branagh is playing the role of the exiled Duke of Milan, Prospero, who uses magic to conjure a storm that shipwrecks his treacherous brother Antonio and the King of Naples, Alonso on his island.
The play ends with Prospero forgiving his brother, after an elaborate revenge scheme involving romance and a murder plot.
The King also sat near Sir Richard Eyre, who directed the performance for the RSC.
Spectators peered down from the seating in the dress circle inside the auditorium to see the King in his seat, while others in the stalls got their phones out to take pictures.
King Charles has been the patron of the RSC since 2024. Before him the late Queen Elizabeth II held the patronage since the company's creation in 1961.
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During the interval, the King met the RSC's in-house costume department and admired a crown used in the company's production of Edward II last year.
He also touched the fabric of a dress worn by Dame Judi Dench in All's Well That Ends Well in 2003.
Next, he marvelled at a robe and gown worn by David Tennant in his role in Richard II in 2013, and a costume worn by Sir Antony Sher in a 1984 production of Richard III.
The King said the costumes were "brilliant".
The Tempest, which was one of the last plays written by Shakespeare, is running at the theatre until June 20.
Co-artistic directors of the RSC, Mr Evans and Ms Harvey said it was a "tremendous honour to welcome His Majesty the King back to the Royal Shakespeare Theatre for this landmark production of The Tempest".
(c) Sky News 2026: King surprises audience at production of Shakespeare's The Tempest
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