Catherine, Princess of Wales, is presiding over her yearly festive musical service at the iconic London venue, with guests including royals, celebrities and local heroes who have supported their local areas.
The sizable congregation will enjoy a selection of traditional hymns, orchestral pieces, and literary excerpts from performers including award-winning actors.
The theme of the service, held in the glowing Westminster Abbey on Friday afternoon, is generosity and expressing affection towards one's neighbour.
Among the guests will be a couple named the Cordiners, whose young girl was lost to a tumour, and who established a foundation, a support fund, to help households where there is a youngster facing a life-limiting condition.
"The time, care and compassion you give, often without fanfare or recognition, and without any hope for reward or acknowledgement, make an profound impact to the lives of others," Her Royal Highness stated in a letter ahead of the carol service.
The Princess of Wales is continuing her own steady comeback to official duties after her cancer diagnosis and chemotherapy, last month delivering her first public speech for two years, in which she talked about recognising the "selfless, commonly overlooked efforts of carers".
Those coming to the Abbey will enjoy performances from young musicians backed by the Future Talent charity, set up with the help of the late Duchess of Kent to widen access to instrumental training.
Carys Wood, aged 18, who plays the trumpet and is from Wales, has been assisted by the charity, with grants helping towards instruments, tuition, and transportation expenses - and she said it was "awesome" to be performing at tonight's service.
"Musical pursuits are frequently pricey," the musician remarked. She is now studying at the prestigious music academy, and added that "all people deserve the chance" to develop their musical skills.
Eliza, Carys's sister who is 11, who plays the euphonium, will be present at the Abbey. "It's unbelievable that I get to perform here in front of so many distinguished guests," she said.
Attending the service will be individuals spanning multiple eras.
That will encompass young Saphia Turner, nine, winner 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 adorned with specially made wreaths, with TV cook Mary Berry and florist Simon Lycett helping to make them.
The musical lineup includes singer Katie Melua, the Westminster Abbey choristers and a nautical singing ensemble, the 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 ITV1 on Christmas Eve.
Morgan is a tech journalist and electronics hobbyist with over a decade of experience in reviewing gadgets and sharing DIY guides.