For the occasion, Kate, who hosted the charity event supported by The Royal Foundation, donned an all-white ensemble featuring—with a long white Catherine Walker coat over a sweater and a pair of high-waisted Holland Cooper pants. The Prince of Wales, George and Louis twinned in navy suits, while Charlotte sported a burgundy, wool dress coat and black tights—the same outfit she wore to last year's service.
During this year's event, which also benefited the Royal Foundation Centre for Early Childhood, George, Charlotte and Louis were all seen depositing letters in a red post box was set up to collect cards and messages from the church's congregation to be given to children in need.
"Such a special evening with @earlychildhood here at Westminster Abbey, joining so many wonderful people who do so much to support babies and children in our communities," the Prince and Princess of Wales said on Instagram, alongside a photo of their kids holding candles inside the church. "The role of the early years workforce in #ShapingUs is so important, building supportive, nurturing worlds around children and the adults in their lives."
Footage from the service—which also includes musical performances from Adam Lambert, Freya Ridings and Beverley Knight—is set to air as part of the Royal Carols: Together At Christmas special on the U.K.'s ITV channels on Christmas Eve. It will also contain a pre-taped introduction from Kate.
"Join me this Christmas Eve for a special carol service," the princess said in a clip released hours before the event, "as we say a heartfelt thank you to all those supporting the very youngest members of our society during those crucial early years."
See photos of the Royal family at the Together at Christmas carol service below: