Her Royal Highness has organised her yearly Yuletide celebration at the historic Abbey, with a congregation comprising members of the royal family, famous faces, and community champions who have supported their local areas.
The 1,600 guests will listen to a selection of carols, music and readings from stars like Chiwetel Ejiofor and Kate Winslet.
The central message of the concert, held in the candle-lit Abbey on Friday afternoon, is generosity and expressing affection towards one's neighbour.
In the audience are Jonathan and Anna Cordiner, whose daughter died of a tumour, and who established a foundation, Kayleigh's Wee Stars, to aid parents with a terminally ill child.
"The time, care and compassion you give, often without fanfare or recognition, and without any thought of thanks or praise, make an remarkable change to the lives of others," the Princess expressed in a message before 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 major oration since 2023, in which she reflected on recognising the "quiet, often invisible work of caring".
Those coming to the Abbey can listen to talented youth performers supported by the charitable trust Future Talent, set up with the help of the Duchess of Kent to widen access to musical tuition.
Carys Wood, aged 18, who plays the trumpet and is from southwest Wales, has been helped by the organisation, with awards contributing to musical instruments, lessons and travel costs - and she said it was "amazing" to be playing at tonight's service.
"Pursuing music is often costly," Carys said. She is now enrolled 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 likewise attend the Abbey. "I never thought I'd be able to play there in front of so many important people," she said.
Among the guests will be representatives of different generations.
That will feature nine-year-old Saphia Turner, recipient of a young hero award, who sells artwork and carries out sponsored challenges to raise money for local food charities.
The Abbey has been festooned with custom-created holiday decorations, with celebrity baker Mary Berry and floral designer Simon Lycett assisting in their creation.
Taking to the stage will be recording artist Katie Melua, the Abbey's own choir and a nautical singing ensemble, Fisherman's Friends, who said the chance to take part was "the icing on the cake for us."
The festive event titled 'Together at Christmas' will be aired by a major network on Christmas Eve.
Lena ist eine preisgekrönte Autorin und Schreibcoach mit über zehn Jahren Erfahrung in der Förderung literarischer Talente.