Christine Baranski Agnes van Rhijn Actor Cynthia Nixon Ada Brook Actor Carrie Coon Bertha Russell Actor Morgan Spector George Russell Actor Denée Benton Peggy Scott Actor Louisa Jacobson Marian Brook Actor Taissa Farmiga Gladys Russell Actor Blake Ritson Oscar van Rhijn Actor Simon Jones Bannister Actor Harry Richardson Larry Russell Actor Thomas Cocquerel Tom Raikes Actor Jack Gilpin Church Actor Julian Fellowes Executive Producer Gareth Neame Executive Producer Michael Engler Executive Producer