Adam Lambert
Adam Lambert performed "The Christmas Song" alongside British singer-songwriter Beverley Knight at the "Royal Carols: Together at Christmas" concert on Dec. 8, 2023. Photo: Adam Lambert/Instagram Adam Lambert/Instagram

Adam Lambert shared his gratitude to Kate Middleton for inviting him to perform at the third annual "Royal Carols: Together at Christmas" concert at Westminster Abbey on Friday, December 8.

The singer admitted that it was surreal and "flattering" to sing inside the historic abbey in front of royal family members. He performed "The Christmas Song" alongside British singer-songwriter Beverley Knight.

One of the attendees said that Kate Middleton and Prince William's children, Prince George, Princess Charlotte and Prince Louis "watched intently" as they performed, which was followed by a Bible reading by the Prince of Wales.

Lambert said that he got to meet the Princess of Wales ahead of his performance. He told People of the experience: "I had the honor of meeting Catherine, Princess of Wales. She invited the performers she wanted to see at the service, and it was lovely to visit with her before we performed."

The "American Idol" alum said this is not the first time he has performed for the royal family having sang at Queen Elizabeth II's Platinum Jubilee celebrations in June last year. But this time he performed at a serene setting at Westminster Abbey, where King Charles III had his coronation on May 6 this year and where Kate Middleton and Prince William wed in 2011.

"I've performed for the royals during the Queen's Jubilee but they were quite far away on the other side of the crowd. So this will be sort of up close and personal and hopefully bringing Christmas cheer to people that tune in on Christmas Eve," Lambert shared.

As to the atmosphere inside Westminster Abbey, he said it was "very still, which added a calmness" to his energy. He said the song he performed "felt sort of like a lullaby".

He shared: "I've always loved history and old architecture, and this is sort of my sweet spot. I was able to walk around a little bit after my rehearsal and just kind of take a little self-guided tour of some of the areas inside at the Abbey and it's just breathtaking, and the amount of history in here is nuts."

The "Whataya Want from Me" hitmaker added: "You know you have the tombs of monarchs and poets and other iconic historical figures, so it's pretty wild. It's such an honor to be performing at the Westminster Abbey, a place that I've seen on television and in photos for years but have never been to myself, so it is quite breathtaking."

Lambert said it was a "really flattering invite to receive" from Kate Middleton to sing at the "Royal Carols: Together at Christmas" concert. He shared his hope that she enjoyed what they had "in store for her". The event will be broadcast on ITV1 and ITVX on Christmas Eve.