Trust GCHQ ???
Who in their right mind would trust them - they have proven themselves to be completely untrustworthy.
Lying is their stock in trade - even the name is a lie GCHQ - Government Communications Headquarters which tries to give the impression that it is used for this government's communications whereas its actual job is to spy on other peoples communications.
When there is a suitably long record of them behaving ethically and following the rules (100 years should suffice!!!) then people might start to believe them - until then they have even less credibility than a politician.