The Duchess of Cambridge had a special gift for royal fans this holiday season. Kate treated Royal Carols: Together at Christmas viewers to a surprise piano performance. The royal mom of three accompanied Tom Walker on the piano as he performed his poignant new song “For Those Who Can’t Be Here” during the program, which aired on Christmas Eve—watch the full performance below!

Tom has described his and the royal’s duet as a “once in a lifetime experience.” “I thought she absolutely smashed the performance; it’s not easy to just jump behind a piano with a bunch of musicians you’ve never played with before and record live takes to camera, but she completely nailed it,” the Scottish singer said, according to ITV.

Tom told The Sun that the song has “jumped 57 places in the charts.” “It was so well received, I probably owe her royalties now. She sent me a letter thanking me for the opportunity but it should be me thanking her,” he shared. “It was a wonderful experience and she was so warm. She made the effort to thank all the musicians but it was us who felt so grateful to be part of something so special.”

The Duchess hosted and spearheaded the carol concert. The service was filmed earlier this month at London’s Westminster Abbey, although Kate’s performance was recorded the day before.

Following the broadcast on Christmas Eve, the Cambridges’ social media accounts shared a message that read: “Together at Christmas brought together so many inspirational individuals for a night of wonderful carols and music. But above all, it was about celebrating the goodwill, acts of kindness, love, empathy, and compassion which have helped people come through these difficult times.”