Her Royal Highness has organised her annual Yuletide celebration at Westminster Abbey, with guests including members of the royal family, famous faces, and community champions who have helped their communities.
The sizable congregation will hear a mix of carols, music and readings from performers including Chiwetel Ejiofor and Kate Winslet.
The focus of the service, held in the candle-lit Abbey on Friday afternoon, is compassion and demonstrating care for others.
Attending the event are Anna and Jonathan Cordiner, whose daughter died of a tumour, and who set up a charity, a support fund, to aid parents with a terminally ill child.
"The dedication, empathy, and kindness you show, often quietly and unspoken, and without any expectation or recognition, make an remarkable change to the circumstances of individuals," wrote Catherine in a message before the concert.
The princess has been making her own steady comeback to public life after her cancer diagnosis and chemotherapy, last month delivering her major oration since 2023, in which she discussed recognising the "selfless, commonly overlooked efforts of carers".
Those coming to the Abbey will be entertained by budding artists aided by the Future Talent organisation, set up with the help of the former royal to increase availability of music lessons.
Carys Wood, aged 18, who plays the trumpet and is from Wales, has been supported by the organisation, with awards contributing to musical instruments, lessons and travel costs - and she said it was "incredible" to be playing at the concert.
"Pursuing music is often costly," the musician remarked. She is now enrolled at the renowned conservatoire, and added that "everyone should have the opportunity" to develop their musical skills.
Eliza, Carys's sister who is 11, who plays the euphonium, 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 young Saphia Turner, nine, recipient of a prize for youthful altruism, who produces drawings and undertakes charity feats to collect donations for community pantries.
The Abbey has been decorated with custom-created holiday decorations, with TV cook Mary Berry and florist Simon Lycett contributing to their design.
The musical lineup includes recording artist 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 perfect culmination."
The Together at Christmas carol concert will be broadcast on a major network on Christmas Eve.
Maya Chen is a gaming industry analyst and writer specializing in online casinos, with expertise in Canadian gaming regulations and player trends.