Her Royal Highness has organised her yearly Yuletide celebration at the iconic London venue, with attendees featuring royals, celebrities and local heroes who have made a difference in their neighbourhoods.
The 1,600 guests will enjoy a blend of festive songs, musical performances, and spoken word pieces from performers including Chiwetel Ejiofor and Kate Winslet.
The central message of the service, held in the glowing Westminster Abbey on the afternoon, is kindness and showing love to others.
Among the guests will be Anna and Jonathan Cordiner, whose daughter died of a brain tumour, and who founded an organisation, a charity called Kayleigh's Wee Stars, to help households where there is a terminally ill child.
"The dedication, empathy, and kindness you show, often discreetly and without words, and without any thought of thanks or praise, make an remarkable change to the well-being of people," wrote Catherine in a note prior to the carol service.
The Princess of Wales is continuing her own measured re-emergence to public life subsequent to her illness and medical care, in November making her initial major address in two years, in which she reflected on recognising the "quiet, often invisible work of caring".
Those coming to the Abbey will be entertained by young musicians supported by the charitable trust Future Talent, set up with the help of the former royal to widen access to instrumental training.
An 18-year-old named Carys Wood, who performs on the trumpet and is from Wales, has been assisted by the charity, with awards contributing to instruments, tuition, and transportation expenses - and she said it was "incredible" to be taking part in tonight's service.
"Pursuing music is often costly," Carys said. She is now a student at the renowned conservatoire, 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 also be at the Abbey. "It's unbelievable that I get to perform here in front of so many important people," she said.
Within the audience will be individuals spanning multiple eras.
That will encompass nine-year-old Saphia Turner, honouree of a youth community award, who creates and sells art and completes fundraising tasks to generate funds for local food charities.
The Abbey has been festooned with custom-created holiday decorations, with well-known chef Mary Berry and flower expert Simon Lycett assisting in their creation.
Taking to the stage will be Katie Melua, choristers from Westminster Abbey and a Cornish sea shanty group, Fisherman's Friends, who said the opportunity to perform was "the perfect culmination."
The festive event titled 'Together at Christmas' will be televised and shown on television on December 24th.
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