This episode takes place in November 1938. The violent rioting depicted in Germany when Persie calls appears to be the Kristallnacht, which occurred throughout Nazi Germany on November 9 and 10 ,1938.
Claire Foy (Lady Persephone Towyn) & Ed Stoppard (Sir Hallam Holland) also worked together on The Crown (2016) as Queen Elizabeth II & Tony Longdon respectively.