Catherine, Princess of Wales, is presiding over her annual festive musical service at Westminster Abbey, with guests including members of the royal family, famous faces, and community champions who have supported their local areas.
The sizable congregation will enjoy a selection of traditional hymns, orchestral pieces, and literary excerpts from actors such as Kate Winslet and Chiwetel Ejiofor.
The central message of the concert, held in the candle-lit Abbey on Friday, is compassion and demonstrating care for others.
Among the guests will be a couple named the Cordiners, whose young girl was lost to a brain cancer, and who founded an organisation, Kayleigh's Wee Stars, to support families who have a youngster facing a life-limiting condition.
"Your efforts, love, and understanding, often without fanfare or recognition, and without any expectation or recognition, make an remarkable change to the well-being of people," wrote Catherine in a note prior to the carol service.
The royal has been undertaking her own steady comeback to official duties after her cancer diagnosis and chemotherapy, recently giving her first public speech for two years, in which she discussed recognising the "discreet, frequently unseen labour of caregivers".
Attendees entering the Abbey will enjoy performances from talented youth performers aided by the Future Talent organisation, set up with the help of the Duchess of Kent to widen access to musical tuition.
An 18-year-old named Carys Wood, who plays the trumpet and is from southwest Wales, has been supported by the organisation, with grants helping towards instruments, tuition, and transportation expenses - and she said it was "incredible" to be performing at the evening's event.
"Pursuing music is often costly," the musician remarked. She is now studying at the Royal Academy of Music, and added that "all people deserve the chance" to develop their musical skills.
Carys's 11-year-old sister, Eliza, who is a euphonium player, will also be at the Abbey. "I never thought I'd be able to play there in front of so many important people," she said.
Within the audience will be representatives of different generations.
That will encompass young Saphia Turner, nine, recipient of a youth community award, who produces drawings and undertakes charity feats to raise money for local food charities.
The Abbey has been decorated with custom-created holiday decorations, with celebrity baker Mary Berry and floral designer Simon Lycett assisting in their creation.
The musical lineup includes singer Katie Melua, the Westminster Abbey choristers and a Cornish sea shanty group, the Fisherman's Friends, who said the invitation to sing was "the perfect culmination."
This annual carol service will be broadcast on ITV1 on Christmas Eve.