Claire Foy (seasons 1–2, featured season 4, guest season 5), Olivia Colman (seasons 3–4), and Imelda Staunton (season 5-6) - Queen Elizabeth II

Serena Scott Thomas - Kelly Bridges (seasons 1 & 2; guest season 3)

Annette O'Toole - Lisa Bridges (seasons 1 & 2; guest seasons 3 & 4)

Kelly Hu - Inspector Michelle Chan (season 3; guest season 4)