The Courier

Factual error: During one scene, a police siren can be heard in the background. However, this was 1960/1 and police sirens were not introduced into the UK until 1963. Before that, police cars had bells.

Anthorin

Continuity mistake: The same couple are sitting behind Alex and Greville when they attended Cinderella and Swan Lake ballet at two different times.

Emily Donovan: We know you're a patriot. We know how hard this must be for you. Colonel, whatever brought you here, it must frighten you more than the danger of you being here.
Oleg Penkovsky: Khrushchev. Khrushchev frightens me. He is impulsive, chaotic - a man like that should not have nuclear commands.

Sheila: Sounds like work.
Greville Wynne: No. Tell them I'm in my chair.

Oleg Penkovsky: Greville, we are only two people. But this is how things change.