Her Royal Highness has organised her yearly Yuletide celebration at the iconic London venue, with a congregation comprising royals, celebrities and local heroes who have helped their communities.
The 1,600 guests will enjoy a selection of carols, music and readings from actors such as Kate Winslet and Chiwetel Ejiofor.
The focus of the concert, held in the atmospheric historic church on the afternoon, is kindness and showing love to others.
In the audience are a couple named the Cordiners, whose young girl was lost to a brain cancer, and who set up a charity, a support fund, to aid parents with a youngster facing a life-limiting condition.
"The dedication, empathy, and kindness you show, often quietly and unspoken, and without any thought of thanks or praise, make an remarkable change to the well-being of people," the Princess expressed in a letter ahead of the festive gathering.
The royal has been undertaking her own steady comeback to the public eye subsequent to her illness and medical care, last month delivering her major oration since 2023, in which she discussed recognising the "selfless, commonly overlooked efforts of carers".
Attendees entering the Abbey will be entertained by young musicians aided by the charitable trust Future Talent, set up with the help of the late Duchess of Kent to increase availability of instrumental training.
Trumpeter Carys Wood, 18, who performs on the trumpet and is from Pembrokeshire, has been helped by the organisation, with funding assisting with instruments, tuition, and transportation expenses - and she said it was "amazing" to be performing at the concert.
"Music can be very expensive," she stated. She is now studying at the Royal Academy of Music, and added that "everyone should have the opportunity" to cultivate their performance abilities.
Eliza, Carys's sister who is 11, who performs on the brass instrument, will be present at the Abbey. "I never thought I'd be able to play there in front of so many notable figures," she said.
Among the guests will be people from various age groups.
That will include nine-year-old Saphia Turner, recipient of a youth community award, who creates and sells art and completes fundraising tasks to generate funds for community pantries.
The Abbey has been adorned with specially made wreaths, with well-known chef Mary Berry and flower expert Simon Lycett contributing to their design.
Taking to the stage will be singer Katie Melua, the Westminster Abbey choristers and a nautical singing ensemble, Fisherman's Friends, who said the invitation to sing was "a dream come true."
This annual carol service will be broadcast on television on December 24th.
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