Thinking about this a bit more I can see a second series. The main beneficiaries are the police and the acting Home Secretary who is now PM. They had the most to gain from sideling the security forces. They also dropped the new terror laws that the assainated Home Secretary wanted introduced.
So...
In the frame for being the bad guys, but ultimately not involved. They knew there was a police informer but not who. Backed the Home Secretary because she was going to introduce tougher laws to fight crime, which would have marginalised the police and given them greater powers. Ultimately lost...
Very tense in parts but ultimately felt all a bit rushed and contrived. Did not buy the potential suicide bomber being the bomb maker as she would have been too valuable to play that role. The unseen wife’s boyfriend was a red herring. Generally though a good series but all loose ends tied, so...
Been wondering that myself, if so who is he going to trust to leave the evidence he took from Julia's house. Looks like to me the last episode is going to leave puzzles and however is responsible getting off and set up a second series.
The security forces thought they had control of the asset in Julia until she went off script by taking the information they gave to the PM to blackmail him. I think they realised there was a leak at the police counter terrorism end. However they underestimated her ambition to over throw the PM...
My guess is the bodyguard is being set up by the security forces or Number ten. It will be interesting to see who the wife's boyfriend is and if they have anything to do with the plot. Is the Home Secretary dead? I would not be surprised as the writer has a habit of killing off lead characters...