The Princess of Wales is hosting her annual Yuletide celebration at the iconic London venue, with a congregation comprising dignitaries, stars, and everyday helpers who have supported their local areas.
The sizable congregation will hear a blend of carols, music and readings from performers including Chiwetel Ejiofor and Kate Winslet.
The focus of the service, held in the atmospheric historic church on the afternoon, is generosity and expressing affection towards one's neighbour.
In the audience are a couple named the Cordiners, whose daughter died of a tumour, and who founded an organisation, Kayleigh's Wee Stars, to support families who have a child with a terminal illness.
"Your efforts, love, and understanding, often without fanfare or recognition, and without any expectation or recognition, make an remarkable change to the circumstances of individuals," wrote Catherine in a note prior to the festive gathering.
The royal has been undertaking her own measured re-emergence to the public eye subsequent to her illness and medical care, in November making her first public speech for two years, in which she talked about recognising the "discreet, frequently unseen labour of caregivers".
Attendees entering the Abbey will enjoy performances from budding artists backed by the Future Talent charity, co-founded by the Duchess of Kent to widen access to musical tuition.
Carys Wood, aged 18, who is a trumpet player and is from southwest Wales, has been supported by the organisation, with awards contributing to equipment, teaching, and travel fees - and she said it was "awesome" to be taking part in tonight's service.
"Pursuing music is often costly," the musician remarked. She is now enrolled at the prestigious music academy, and added that "all people deserve the chance" to hone their artistic talents.
Her younger sibling Eliza, aged 11, who performs on the brass instrument, will likewise attend the Abbey. "It's unbelievable that I get to perform here in front of so many important people," she said.
Attending the service will be individuals spanning multiple eras.
That will include nine-year-old Saphia Turner, winner of a prize for youthful altruism, who creates and sells art and completes fundraising tasks to collect donations for food banks.
The Abbey has been adorned with custom-created holiday decorations, with TV cook Mary Berry and florist Simon Lycett helping to make them.
Among the musical performers will be singer Katie Melua, the Westminster Abbey choristers and a maritime folk band from Cornwall, the group Fisherman's Friends, who said the invitation to sing was "the icing on the cake for us."
This annual carol service will be televised and shown on ITV1 on Christmas Eve.
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Angela Ryan
Angela Ryan