According to their website, the Girls Friendly Society provides "opportunities for girls and young women to develop their self-esteem, emotional well being and resilience" in the UK. It was begun by the Anglican Church in 1875.
Eunice is said to be age fifteen.
It is said to be 1939.
Claire Foy (Lady Persephone Towyn) & Ed Stoppard (Sir Hallam Holland) also worked together on The Crown (2016) as Queen Elizabeth II & Tony Longdon respectively.