Jenna Coleman and Tom Hughes sang a few of German songs. Jenna Coleman admitted on Late Show with Seth Meyers she wanted to back out and emailed to be dubbed. In the end she did her own singing. Neither are fluent in German. She later sang a few lines of an English carol in the Christmas Special.
The song Victoria sings with Albert accompanying her at the piano is Franz Schubert's lied "Du bist die Ruh'" (You are rest and peace).
The Thames Tunnel in this episode is a tunnel beneath the River Thames in London, connecting Rotherhithe and Wapping. It measures 35 ft (11 m) wide by 20 ft (6.1 m) high and is 1,300 ft (400 m) long, running at a depth of 75 ft (23 m) below the river surface measured at high tide. It is the first tunnel known to have been constructed successfully underneath a navigable river. It was built between 1825 and 1843 by Marc Brunel and his son Isambard using a tunneling shield newly invented by Marc and Lord Thomas Cochrane.