Katherine Jenkins and JB Gill celebrate Christmas with 5,000 Songs of Praise viewers by singing carols in the Royal Albert Hall, including Ding Dong Merrily on High and The Twelve Days of Christmas. Katherine and JB also give their own special performances and reveal the story behind Trafalgar Square's Christmas tree. Music: Ding Dong! Merrily On High 12 Days of Christmas Angels from the Realms Silent Night Hark the Herald Angels Sing.