Her Royal Highness has organised her yearly festive musical service at Westminster Abbey, with guests including members of the royal family, famous faces, and community champions who have made a difference in their neighbourhoods.
The sizable congregation will hear a selection 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, is compassion and demonstrating care for others.
Attending the event are Anna and Jonathan Cordiner, whose daughter died of a brain cancer, and who set up a charity, a support fund, to support families who have a terminally ill child.
"Your efforts, love, and understanding, often discreetly and without words, and without any expectation or recognition, make an remarkable change to the lives of others," Her Royal Highness stated in a note prior to the concert.
The princess has been making her own steady comeback to the public eye after her cancer diagnosis and chemotherapy, in November making her initial major address in two years, in which she discussed recognising the "selfless, commonly overlooked efforts of carers".
Guests arriving at the Abbey can listen to talented youth performers backed by the Future Talent charity, set up with the help of the late Duchess of Kent to widen access to instrumental training.
Trumpeter Carys Wood, 18, who performs on the trumpet and is from Wales, has been supported by the charity, with grants helping towards musical instruments, lessons and travel costs - and she said it was "awesome" to be performing at tonight's service.
"Pursuing music is often costly," the musician remarked. She is now a student at the renowned conservatoire, and added that "each individual ought to be given the possibility" to develop their musical skills.
Carys's 11-year-old sister, Eliza, 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 distinguished guests," she said.
Among the guests will be people from various age groups.
That will include Saphia Turner, aged nine, winner of a prize for youthful altruism, who produces drawings and undertakes charity feats to collect donations for food banks.
The Abbey has been adorned with specially made wreaths, with TV cook Mary Berry and florist Simon Lycett assisting in their creation.
Among the musical performers will be singer Katie Melua, the Abbey's own choir and a Cornish sea shanty group, the group Fisherman's Friends, who said the invitation to sing was "the icing on the cake for us."
The festive event titled 'Together at Christmas' will be broadcast on ITV1 on Christmas Eve.
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