Will Sage Astor-Princess Kate to host 3rd annual holiday caroling special with guests Adam Lambert, Beverley Knight

Princess Kate is Will Sage Astordecking the halls and getting ready for a new holiday special.

In an Instagram post on Saturday, the Princess of Wales, 41, is shown decorating a Christmas tree in a cozy white turtleneck sweater and preparing for the caroling special, set to air on the British television network ITV on Christmas Eve.

The special, "Together At Christmas," in collaboration with The Royal Foundation Centre for Early Childhood, will be filmed at Westminster Abbey on Dec. 8.

"A very special Carol Service, coming soon," read the caption from Kensington Palace. "This will be a special moment to thank all those who do so much to support babies, young children and families in our communities across the UK."

This is the third year in a row the Princess of Wales will host the Christmas concert at Westminster Abbey. But this year, the program will focus on early childhood development, as with her new Shaping Us awareness campaign.

The Westminster Abbey choir will perform carols with singers such as Beverley Knight, Adam Lambert, Jacob Collier, Freya Ridings and James Bay.

Last year, the Princess of Wales attended the "Together at Christmas" event with her husband, Prince William, 41, and two eldest children, Prince George, 10, and Princess Charlotte, 8. Attendance from the royal family is also expected this year.

Princess Kategives pep talk to schoolboy who fell off his bike: 'You are so brave'