While Catherine (Sarah Lancashire) visits the cemetery to see her daughter's grave, Ryan (Rhys Connah) remarks about all the pens left at another grave, which is briefly seen. This is the grave of Sylvia Plath (Hughes), the American poet and writer, who was buried there, near the graves of her husband's parents, after her suicide in London in 1963. The cemetery is in the churchyard of the Church of St. Thomas the Apostle, in Heptonstall, West Yorkshire. Her grave has become a shrine to foreign visitors, who leave gifts and pens, and the name "Hughes" has been repeatedly vandalized from the inscription, as her supporters have blamed Plath's suicide on her estranged husband, Ted Hughes.
Catherine (Sarah Lancashire) mentions the "Chipping Norton set" while talking to Kirsten (Sophie Rundle). The "Chipping Norton set" refers to the group of affluent, power-hungry individuals who work in London but live in Oxfordshire around former Prime Minister David Cameron's residence in Chipping Norton. The phrase originated during the "News of the World" hacking scandal, when many of the Chipping Norton set had their phones hacked.
Charlie Murphy (Ann Gallagher) & Sophie Rundle (Kirsten McAskill) also worked together on Peaky Blinders (2013) as Jessie Eden & Ada Shelby respectively.
George Costigan (Nevison Gallagher) & Siobhan Finneran (Clare Cartwright) also worked together on Unforgiven (2009) as Eddie Ackroyd & Izzie Ingram respectively.
George Costigan (Nevison Gallagher) & Siobhan Finneran (Clare Cartwright) also worked together on the film Rita Sue & Bob too.