Excellent BBC series kinda reminds me of LeCarres "Smileys People" which I thought was excellent.Typical British in that you have no idea of what the hell is going on till another piece of the puzzle is given away with each episode untill it all finally comes together.If your interested this link will let you catch up on what you may have missed to date.
http://www.pbs.org/wgbh/masterpiece/lastenemy/index.html

I stumbled upon this a few weeks ago and have really enjoyed it.

Thanks for the link. Now I think I can really follow the story.