London musician Charlotte Campbell had a shock when the star sent her a message of support.
Downton Abbey is set to release its first ever Christmas album.
Christmas at Downton Abbey features 45 tracks on two discs, and is to be released next month.
The album will feature hymns, carols and Christmas songs, as well as a festive version of Downton Abbey's theme tune.
Actors in the series will also perform on the album, including Elizabeth McGovern (Countess of Grantham), Julian Ovenden (Charles Blake) and Jim Carter (Carson).
McGovern said: "It was so exciting for me to have been given the opportunity to sing two songs in a totally different context to that which I'm accustomed - without my guitar, without my band."
Other songs on Christmas at Downton Abbey are performed by musicians including Dame Kiri Te Kanawa and the Choir of Kings College, while Carter reads the popular Christmas story 'Twas the Night Before Christmas.
Christmas at Downton Abbey will be released on November 10.