The Princess of Wales is hosting her customary Yuletide celebration at Westminster Abbey, with a congregation comprising members of the royal family, famous faces, and community champions who have helped their communities.
The sizable congregation will listen to a mix of festive songs, musical performances, and spoken word pieces from stars like award-winning actors.
The theme of the service, held in the candle-lit Abbey on Friday, is kindness and showing love to others.
In the audience are a couple named the Cordiners, whose daughter died of a tumour, and who established a foundation, Kayleigh's Wee Stars, to help households where there is a terminally ill child.
"The dedication, empathy, and kindness you show, often quietly and unspoken, and without any expectation or recognition, make an profound impact to the well-being of people," wrote Catherine in a letter ahead of the concert.
The Princess of Wales is continuing her own gradual return to official duties after her cancer diagnosis and chemotherapy, last month delivering her first public speech for two years, in which she reflected on recognising the "quiet, often invisible work of caring".
Guests arriving at the Abbey will be entertained by young musicians aided by the Future Talent charity, set up with the help of the late Duchess of Kent to increase availability of musical tuition.
An 18-year-old named Carys Wood, who is a trumpet player and is from southwest Wales, has been assisted by the organisation, with awards contributing to musical instruments, lessons and travel costs - and she said it was "awesome" to be playing at tonight's service.
"Musical pursuits are frequently pricey," the musician remarked. She is now enrolled at the prestigious music academy, and added that "everyone should have the opportunity" to cultivate their performance abilities.
Carys's 11-year-old sister, Eliza, who performs on the brass instrument, will also be at the Abbey. "It's unbelievable that I get to perform here in front of so many distinguished guests," she said.
Among the guests will be representatives of different generations.
That will encompass young Saphia Turner, nine, honouree of a youth community award, who sells artwork and carries out sponsored challenges to collect donations for local food charities.
The Abbey has been decorated with specially made wreaths, with celebrity baker Mary Berry and floral designer Simon Lycett helping to make them.
Among the musical performers will be Katie Melua, choristers from Westminster Abbey and a nautical singing ensemble, Fisherman's Friends, who said the chance to take part was "the icing on the cake for us."
The Together at Christmas carol concert will be broadcast on a major network on Christmas Eve.
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