As usual it always comes down to, "Give 'em an inch...".
They paint so much lipstick on their pig but fact is that no matter what powers they manage to finagle out of the government they will never be happy until they have the right to know every tiny detail about our lives at the push of a buttonm, preferably with no government oversight. The really sad fact is they don't do it 'cos they need the info as they claim, they do it to ensure they can secure their dept budgets each year. GCHQ, MI5, MI6, etc are like any other company dept, they need to justify their worth in their yearly review and claiming they've foiled and caught X number of terrorists, paedos and other ne'er do wells is what they have to do.
I fully support the fact that we need secret services to keep the country and our enemies under a watchful eye but "ei incumbit probatio qui dicit, non qui negat" ( 'the burden of proof is on the one who declares, not on one who denies' ).