BBC One's drama will return for six more episodes later this year, with its second series taking place in 1923.
John Simm and Maxine Peake will return as John and Grace Middleton, while newcomer Tom Varey has joined the cast as their adult son Bert.
Julian Sands (24) has also signed up to play Lord Kilmarnock, while Waterloo Road's Phoebe Dynevor will play the station master's daughter Phoebe.
Also joining the cast are Ben Batt (Shameless) as landowner Alf Rutter, Derek Riddell (Ugly Betty) as Labour candidate Robin, Juliet Aubrey (The White Queen) as Marie Stopes advisor Joy Dangerfield, Daniel Ezra as boxer Ghana Jones, Alex Robertson as Robert Read and Andrew Gower (Being Human) as Bert's friend Gilbert Hankin.
Juliet Stevenson, Rupert Evans and Emily Beecham are among the cast members returning for the second series.
Full broadcasts dates for the second series will be confirmed at a later date.