The scene with Tommy and Ada in the library, is actually John Rylands Library in Manchester.
Paddy Considine also plays in the clip of the Arctic Monkeys song 'Leave before the lights come on'. In this episode and many others, various Arctic Monkeys songs can be heard.
Grand Duke Leon Petrovich Romanov appears in this episode. He is not an historical figure, though his story is somewhat similar to the historical figure Prince Roman Petrovich of Russia who was also saved by the HMS Marlborough. However, Prince Roman Petrovich is much younger and wasn't married at the time period of Season 3. The butler mentions a meeting with Grand Duke Michael Mikhailovich of Russia, and Prince Vsevolod Ivanovich of Russia. Both are historical figures who were exiled in England at the time.