Maria Doyle Kennedy sings in this episode. She has a long history of performing, including being in the Irish band Hothouse Flowers and acting in the film The Commitments (1991), where she played a singer named Natalie.
Maria Doyle Kennedy (Siobhan Sadler) and James Frain (Ferdinand Chevalier) have previously worked together in the TV show The Tudors (2007). They played Queen Catherine of Aragon and Thomas Cromwell, respectively.