BTW,there is a series by the BBC titled "MI-5" that is about that organization,and is some of the best tv you will ever see. Can be streamed from Netflix,Amazon,etc,etc,etc.
VERY interesting look into how other governments deal with domestic crimes,which sometimes spill over into international crimes.
Some of the best writing and acting I have ever seen,and just like in real life,none of the detectives are immune from what can happen in real life.