... I shall say this only once...
...PI said that GCHQ is starting to see itself as “above the law”....
The security apparatus of this country (which includes GCHQ, Security Service and Secret Intelligence Service) is a hangover from WW2.
At the end of WW2 our military was not completely disbanded, but switched into providing defence during the 'Cold War'. Essentially, much of the military structure was kept going, which was good for those who had a job in it. So Britain ran these services, essentially as in WW2, right up to the middle of the 1990s, which was when the Cold War ended.
Since then, the people working in this area have been frantic to keep their jobs, and have tried to justify them by looking for other things to do - crime, or terrorism.
At this point it is instructive to look at the position that a Secret Service holds in a democracy. Normally, democratic institutions HAVE to be open - you can't run a democracy any other way. But in times of crisis - during a war when there is a danger of invasion, for instance, even democracies need systems to provide immediate executive action with no democratic balances. They may need to lock someone up who has committed no crime, for instance. The bodies set up to do this are by definition 'above the law' - they have no requirement to have democratic oversight or to abide by any legal restrictions. They can't be challenged in the courts. This is where the SS, SIS and GCHQ were born.
It is not true to say that these organisations are "starting to see themselves as above the law”. They were always above the law from their inception. The oddity is that, in the absence of any critical threat to the existence of the nation, these bodies are still trying to justify their existence, and laws are being bent to achieve this.
If you need an illustration of this, look at the court cases which the Security Service has tried to bring. Even with the benefit of draconian legislation and administrative banning orders, they usually fail. The way Security Service works is completely alien to the way, for instance, that the Police work. The Police investigate a case, suspect a person, amass evidence, arrest someone and pass the accused to a court. Security Service suspect someone, imprison them, and then try to extract information from them with no interest in due process.
There is certainly a current terrorist threat - though considerably less than the Irish threat in the 1970s. At that time the Police, suitably staffed and supported, were quite capable of dealing with it. That is what should be put in place today, and the wartime security apparatus closed down. We no longer maintain a Bomb Targeting Committee - in the same way we should no longer maintain an extra-legal state enforcement arm.