The dancing fever appeared to spread to the rest of the Royal Box as the Queen, the Prince and Princess of Wales, Princess Charlotte and Prince George all joined in – waving mini Union flags and singing along.
Katy Perry told crowds how excited she was to be in the UK for the Coronation, adding she had brought her mother to the event.
“I am so happy to be here with you people, I love you so much.
“I am so happy to celebrate this whole weekend – I got to bring my mom, she was so happy to be here.
“I would like to dedicate this next song to the King and to the work we get to do together for the British Asian Trust and the Children’s Protection Fund. Thank you for bringing out the firework in so many young people.”
It’s then straight into Perry’s 2011 classic Firework and its memorable chorus, as lasers and smoke illuminated the stage.
The cameo marks the continuation of an unlikely bromance between the King and Mr Richie. On Thursday, Mr Richie entertained the King and Queen during a garden party at Buckingham Palace ahead of the Coronation.
The US singer described his performance at Windsor Castle as a “once-in-a-lifetime opportunity” as he joined thousands of guests at the palace for the first traditional garden party of the King’s reign.