Prince William has delivered an emotional tribute to his “Pa”, the King, before joking around in the stands at a star-studded concert at Windsor Castle.

Addressing a crowd of thousands gathered for the Coronation Concert, the Prince of Wales also offered a sweet reference to his late grandmother, Queen Elizabeth.

“Pa, we are all so proud of you,” William said.

“I know she (the late queen) is up there, fondly keeping an eye on us.

“She would be a very proud mother.”

The prince’s speech before a crowd of 20,000 revellers at the Windsor Castle gala – where the royal family gathered en masse to watch singers such as Katy Perry and Lionel Richie – also highlighted his father’s service and achievements.

“For over 50 years, in every corner of the UK, across the Commonwealth and around the world, he has dedicated himself to serve others, both current and future generations, and those whose memory must not be neglected,” William said.

“Perhaps most importantly of all, my father has always understood that people of all faiths, all backgrounds, and all communities, deserve to be celebrated and supported.”

William finished with his own pledge.

“I also want to express my pride and gratitude for the millions of people who serve, in the forces, in classrooms, hospital wards and local communities,” he said.

“I wish I could mention you all. Your service inspires us. And tonight we celebrate you too.

“I commit myself to serve you all. King, country and Commonwealth. God save the King!”

There were plenty of lighter moments as the concert got underway.

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The King and Queen – colour-coordinated in blue, with the Queen in a royal blue jumpsuit – smiled and waved own flags.

The Princess of Wales sat with her two oldest children, Prince George and Princess Charlotte. Her youngest son – and potential scene-stealer – Prince Louis, who has just turned five, was absent.

At one point, William waved a Union Jack in front of an amused Prince George. He tried the same with Charlotte, who look rather less impressed.

The royals joined the rest of the crowd in rocking to performances by Richie, Perry, Take That and Nicole Scherzinger.

Top Gun star Tom Cruise delivered a video message from his War Bird plane, saying: “Pilot to pilot. Your Majesty, you can be my wingman any time,” before saluting and banking off.

Muppets stars Kermit and Miss Piggy also gave speeches, with the frog saying he was “honoured” to have been invited to the coronation. Kermit even found his way into the royal box, plonking himself in front of the Duke of Edinburgh.

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The night also featured a collaboration between five Royal patronages – The Royal Ballet, The Royal Opera, the Royal Shakespeare Company, The Royal College of Music and The Royal College of Art – who came together for the first time to perform Somewhere from West Side Story.

It came a day after the King and Queen were crowned at London’s Westminster Abbey on Saturday in Britain’s biggest ceremonial event for 70 years.

Buckingham Palace said the monarch and his wife were “deeply touched by the events of yesterday”.

The King and Queen were “profoundly grateful both to all those who helped to make it such a glorious occasion – and to the very many who turned out to show their support in such numbers in London and further afield”, a representative said.

-with AAP