Branson mentions Sylvia Pankhurst while talking to Sybil. Pankhurst was an activist opposed to the war. She was an early women's rights activist who set up soup kitchens for the poorer women of London, and started a factory making toys so the women would have a place to work. Sylvia and her comrades also worked to defend the right of soldiers' wives to decent allowances while their husbands were away, both practically, by setting up legal advice centers, and politically, by running campaigns to oblige the government to take into account the poverty of soldiers' wives. She was a campaigner for the suffragette movement, a prominent left communist and, later, an activist in the cause of anti-fascism.
The battle depicted is likely the Battle of Amiens, also known as the Third Battle of Picardy, fought between 8-12 August 1918. Amiens marked the opening of a major Allied offensive which would eventually be known as the Hundred Days Offensive and would lead to the end of WWI. While both sides suffered major casualties at Amiens (approximately 120,000 dead and wounded), the Allies were successful in breaking through German lines and advanced approximately 7 miles on the first day. Nearly 50,000 German soldiers surrendered by the end of the battle.
While praying at the Downton village church, which is Anglican, Bates tells Anna, "You should have had a church wedding." This is because in 1918, the Anglican church, like the Catholic church, did not allow church weddings for divorcees, which Bates would be.
Clare Calbraith (Jane Moorsum) & Paul Copley (Mr. Mason) also worked together on On Harbour Street (2014) as Rebecca Shepherd & Malcolm Kenrich respectively.