A tense British thriller in the vein of Spooks which I loved. Also similarly, it's difficult to tell who are the good guys and who are the bad guys. Does the end justify the means? or is there no end? At the heart of this is the ethics of using cutting edge but very real technology by shadowy powers on the periphery of law and government. Paranoid and plausible - a worrying combination.

This show was exceptionally good in the first season. The second season and the third have become unwatchable. I don't know why English TV shows have changed so much in the last few years, but I have found myself watching them far less than I used to.