Her Royal Highness has organised her customary Yuletide celebration at the historic Abbey, with attendees featuring dignitaries, stars, and everyday helpers who have supported their local areas.
The large audience will hear a blend of festive songs, musical performances, and spoken word pieces from performers including Kate Winslet and Chiwetel Ejiofor.
The theme of the event, held in the atmospheric historic church on Friday, is compassion and demonstrating care for others.
Attending the event are Jonathan and Anna Cordiner, whose daughter died of a brain cancer, and who set up a charity, a support fund, to aid parents with a terminally ill child.
"Your efforts, love, and understanding, often quietly and unspoken, and without any expectation or recognition, make an extraordinary difference to the lives of others," Her Royal Highness stated in a message before 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 initial major address in two years, in which she discussed recognising the "discreet, frequently unseen labour of caregivers".
Attendees entering the Abbey will enjoy performances from young musicians aided by the charitable trust Future Talent, established in part by the Duchess of Kent to widen access to music lessons.
An 18-year-old named Carys Wood, who is a trumpet player and is from Pembrokeshire, has been helped by the trust, with grants helping towards musical instruments, lessons and travel costs - and she said it was "amazing" to be taking part in the evening's event.
"Pursuing music is often costly," she stated. She is now enrolled 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. "I never imagined I would perform in front of so many important people," she said.
Within the audience will be representatives of different generations.
That will feature Saphia Turner, aged nine, honouree of a young hero award, who produces drawings and undertakes charity feats to raise money for community pantries.
The Abbey has been festooned with handcrafted festive wreaths, with celebrity baker Mary Berry and floral designer Simon Lycett assisting in their creation.
The musical lineup includes recording artist Katie Melua, choristers from Westminster Abbey and a maritime folk band from Cornwall, Fisherman's Friends, who said the chance to take part was "the perfect culmination."
The Together at Christmas carol concert will be aired by ITV1 on Christmas Eve.
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