Jack Lowden as Siegfried Sassoon

Peter Capaldi as Siegfried Sassoon (Older)

Simon Russell Beale as Robbie Ross

Jeremy Irvine as Ivor Novello

Calam Lynch as Stephen Tennant

Tom Blyth as Glen Byam Shaw

Kate Phillips as Hester Gatty

Gemma Jones as Hester Gatty (Older)

Geraldine James as Theresa Thornycroft

Ben Daniels as Dr. Rivers

Edmund Kingsley as Rex Whistler

Harry Lawtey as Bobby Andrews

Anton Lesser as Stephen Tennant (Older)

Lia Williams as Edith Sitwell

Suzanne Bertish as Lady Ottoline Morrell

Jude Akuwudike as Priest

Joanna Bacon as Lady Sybil Colefax

Matthew Tennyson as Wilfred Owen

David Shields as Alexander Fenton

Julian Sands as Chief Medical Officer

Thom Ashley as Hamo Sassoon

Richard Goulding as George Sassoon

Edward Bennett as T.E. Lawrence

Stacey Lynn Crowe as Nurse

Jamie-Lee Beacher as Nurse

Paddy Rowan as Young Soldier

Kellie Shirley as Singing Girl

Daniel Tuite as Major McCartney-Filgate

Mark Oosterveen as Army Doctor

Steven Pacey as Army Doctor

Joyce Henderson as Matron

Torquil Munro as Pianist

Georgina Rylance as Dorothy Brett

Jonathan Broadbent as Robert Graves

Olivia Darnley as Edith Oliver

Tim Delap as Geoffrey Keynes

Christopher Naylor as Tailor

Orlando Jopling as Conductor

Bobby Robertson as Taxi Driver

Chris Dale as Anglican Priest

Andrew Bradley as Stage Doorman