The Princess of Wales is hosting her annual Christmas carol concert at the historic Abbey, with a congregation comprising royals, celebrities and local heroes who have helped their communities.
The sizable congregation will listen to a blend of carols, music and readings from performers including Kate Winslet and Chiwetel Ejiofor.
The theme 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 daughter died of a brain cancer, and who founded an organisation, a charity called Kayleigh's Wee Stars, to support families who have a youngster facing a life-limiting condition.
"Your efforts, love, and understanding, often quietly and unspoken, and without any thought of thanks or praise, make an extraordinary difference to the circumstances of individuals," wrote Catherine in a message before the festive gathering.
The Princess of Wales is continuing her own gradual return to public life after her cancer diagnosis and chemotherapy, in November making her major oration since 2023, in which she talked about recognising the "selfless, commonly overlooked efforts of carers".
Those coming to the Abbey will be entertained by young musicians aided by the Future Talent organisation, co-founded by the late Duchess of Kent to increase availability of instrumental training.
Trumpeter Carys Wood, 18, who plays the trumpet and is from Wales, has been helped by the organisation, with grants helping towards equipment, teaching, and travel fees - and she said it was "incredible" to be playing at the evening's event.
"Music can be very expensive," Carys said. She is now a student at the Royal Academy of Music, and added that "all people deserve the chance" to hone their artistic talents.
Carys's 11-year-old sister, Eliza, who is a euphonium player, 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 Saphia Turner, aged nine, honouree of a prize for youthful altruism, 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 assisting in their creation.
Among the musical performers will be singer Katie Melua, the Abbey's own choir and a maritime folk band from Cornwall, Fisherman's Friends, who said the opportunity to perform was "a dream come true."
The Together at Christmas carol concert will be broadcast on television on December 24th.