Based upon the real life events of the Russian infiltration of the British security services from around the rise of Nazi Germany through to the early 1960s when the infiltration was exposed and 'agents' fled Britain.
This is not an action spy drama, it's a drama based upon intrigue and strategic thrust and parry - as such it's very successful and weaves a gripping tale. Just what exactly is going on? Whom can we trust? Is this opportunism or another move in the long game, or both...?
The three leads, Lewis, Martin & Pearce each offer nuanced performances that between them create and carry the bulk of the show's dramatic tension - and they each do a fine job of conveying a sense of the 'times they lived in' - times overshadowed by the cold war, memories of fascism and an horrendous world war, and of a looming new world struggling to shake off these attachments and mires of the old world.
The unfolding of the story is a little complicated, with frequent time shifts, which clarify and re-clarify understanding - so this is not a casual viewing show. It demands the audience pay full attention and think about and consider what they're witnessing. It all adds up to a very satisfying experience if you're prepared to invest the time - but mostly, you'll simply get sucked into the story and crave resolution.
On the production side, the world created is a very convincing one depicting, primarily, London in the 60s.
Superb!