John and Barbara Stonehouse are played by real-life husband and wife Matthew Macfadyen and Keeley Hawes.
Kevin McNally again takes the role of Harold Wilson, UK Prime Minister from 1964 to 1970 and 1974 to 1976. McNally previously played Wilson in Lendas do Crime (2015).
Other characters such as Sir Edward Twigg (Rupert Wickham) and Lady Twigg (Emma Davies) were scheduled to be included in the drama, but they were dropped from the final edit.