I wanted to like this. Trailers made it look decent and it was recommended as "absolutely brilliant", but there were so many plot holes and silly situations throughout the series that I just couldn't enjoy it. Dialogue was lacking, characters' actions constantly didn't make any sense, and the whole premise of the story was a bit weak.
To name a few of the plot holes:
-A security detail wouldn't constantly lose track of someone and then do nothing about it.
-The head of MI6 is poisoned and a teenage girl thinks it's a great idea to walk off alone when her dad has just taken up that very same job position?
-The British Secret Service wouldn't just go "oh well, promote him all the way to the top" if intel kept landing in some guys lap mysteriously, without launching a full investigation.
-An ex-military wife wouldn't get all fussy about her husband, literally the head of MI6, not telling her things and having to take phonecalls and meet people.
-Said wife is unlikely to go from "I fully support and love you" to spying on her husband based upon the words of someone she hasn't seen in years within the course of one day.
-A CIA operative is... Unlikely to be mates with their target's wife.
-After being suspected of treason and clearance revoked, this man is not arrested or kept a close enough eye on such that they know where he is and what he's doing at all times??
-The head of MI6 would be smarter than to meet an ex-Russian agent in a public place to physically hand over files/commit treason where anyone might see it.
-The head of MI6 would also be smarter than to use his damn personal phone to 'conspire' with an ex-Russian agent constantly via text and phonecall.
-Said ex-Russian agent would not be completely oblivious to 2 men in boots walking up to her on a wooden deck until they're standing over her.
-A Russian agent abandons her career and spends the next 15 years on the run trying to find the person who killed 5 people she knew? Was she given a job description??
-The British Secret Service(s) and Police combined apparently cannot locate this ex-Russian agent after she has been fully identified, despite her being out and about all over London. They seem to stop trying when convenient for the plot.
-An investigation into treason within the secret service would not allow anyone to just walk in off the street, and then plaster highly confidential/sensitive files all over a big screen when presented with 'evidence' they hadn't even verified beforehand.
I could go on - a lot of things frustrated me. Usually you have to just suspend your disbelief a bit for these kind of shows, but so many unbelievable things happened so often that it was impossible to enjoy. Outstandingly poor writing.