Britain revelled in the coronation of King Charles III on Sunday as it staged a star-studded concert watched by 20,000 people at Windsor Castle and millions more across the country and world.

Charles, 74, and Queen Camilla, 75, watched on from a royal box in the grounds of the castle west of London, as Lionel Richie, Katy Perry and British band Take That topped the bill of performers.

Screens erected nationwide broadcast the televised event -- featuring a 70-piece orchestra, choirs and several unique dramatic performances -- to communities, while organisers said it would also be seen in over 100 countries.

Amid the music and video message tributes from an array of public figures, Prince William took to the stage to pay tribute to his father the day after he was formally crowned king.

Noting his late grandmother, Queen Elizabeth II, was "up there, fondly keeping an eye on us", William added she would be "a very proud mother".

"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," the heir to the throne said.

"Pa, we are all so proud of you."

'Celebrate'

Charles' coronation Saturday as monarch of the United Kingdom and 14 Commonwealth countries was the first in Britain in seven decades.

The glittering Westminster Abbey ceremony, steeped in 1,000 years of tradition and ritual, was attended by global royalty and world leaders, as well as hundreds of UK community and charity representatives.

Thanking all those involved, Buckingham Palace said Charles and Camilla had been "deeply touched" by it.

Monday has been declared a public holiday -- meaning people could enjoy Sunday unencumbered.

Earlier, partygoers flocked to tens of thousands of street celebrations and "Big Lunch" events looking to bring modern Britain's communities closer.

After the post-World War II hardships, street parties were a feature of Queen Elizabeth II's 1953 coronation -- and a memorable part of celebrations for her long reign in 1977 and her platinum jubilee last year.

"It's lovely... you need these things to bring the community together," Annette Cathcart, 67, told AFP at a village hall gathering in Ashley Green, in Buckinghamshire, southern England.

"It's the perfect way to celebrate."

More than 67,000 big lunches were planned, according to organisers Eden Project Communities, with Coronation Quiches -- the specially created, baked savoury tart featuring spinach, broad beans and tarragon -- encouraged.

Prime Minister Rishi Sunak hosted one in Downing Street, inviting community volunteers, Ukrainian refugees and dignitaries including US First Lady Jill Biden.

The British leader was joined by his wife, two daughters and the family dog, Nova, who sported a union flag bandana.

'Wingman'

Attention soon turned to Windsor, where the evening spectacle harked back to previous royal jubilees of the late queen.

Guests waved union flags as senior royals -- including William, wife Kate, and two of their three children -- joined Sunak and other VIPs in the royal box.

"We are delighted and honoured to be joined by our newly crowned King Charles III, whose life-long passion for the arts we will be celebrating throughout the show," host Hugh Bonneville promised the crowd.

"He himself, of course, is a painter, an artist -- the artist formerly known as Prince," Downton Abbey and Paddington actor Bonneville quipped, earning widespread laughs, including from the former Prince of Wales Charles.

An early highlight saw the Royal Ballet, the Royal Opera, the Royal Shakespeare Company, the Royal College of Music and the Royal College of Art combine for a one-off performance.

Lionel Ritchie lit up the show midway through, performing hits like "Easy Like Sunday Morning" and "All Night Long", bringing the royals to their feet.

Hollywood star Tom Cruise, actress Joan Collins and singer Tom Jones all appeared via video message.

"You can be my wingman any time", Cruise told the monarch.

A series of pre-recorded sketches also aired, revealing little-known facts about Charles and included moments from The Muppets and beloved literary character Winnie the Pooh.

The evening also featured "Lighting up the Nation", in which well-known locations across Britain were illuminated using projections, lasers and drone displays.

After reconstituted pop group Take That -- minus former frontman Robbie Williams -- closed out the show, audience member Caroline Mcdonough described it as "incredible... a real once-in-a-lifetime experience".

The 53-year-old, who runs a firm getting the long-term unemployed back into work, told AFP people had been "really enjoying themselves... waving their flags and dancing and singing along, just really going for it".

'This is boring'

The once-in-a-generation coronation comes with Britain gripped by the worst cost-of-living crisis in decades.

The long weekend's cost -- reported to be upwards of £100 million ($126 million) -- has caused disquiet as many struggle with rising bills and widespread strikes.

and the arrest of anti-monarchists even before they had a chance to protest Saturday prompted criticism from rights groups.

The BBC said more than 14 million watched the ceremony on its two main terrestrial channels -- well down on previous major royal occasions.

And it reportedly wasn't all smooth sailing for Charles.

The king grumbled about not being "on time" and that "this is boring" as a hiccup delayed the start of his coronation, according to a lip reader who analysed footage of the monarch for Sky News.