I remember reading an article some years ago by Christopher Hitchens about airport security, a subject he returned to many times, and its fatuous stupidity.
He had made some facial expression interpreted by security personnel as mildly disrespectful, and was hauled out of the queue and given the first degree. The last people you should put in charge of security, I remember him writing (but can't actually find the article now), are the security fraternity.
There is an important point here. It is the bizarre way that the security systems tend to work. They begin to categorise among their biggest threats - not just terrorists - but those who criticise security systems, or reveal aspects of their work, or seem disaffected about them in some way.
It is a strange phenomenon. It takes a particularly well-balanced security psychology to be able to distinguish reasonable criticism from dangerous challenge. It is the besetting sin of the security world.
It explains why some of those who have been criticising the huge new surveillance system on both sides of the Atlantic are given such a hard time when they travel.
That is why the revelations in the Guardian last week matter so much that the security apparatus in the USA and UK have broken the encryption used by the main email providers, to provide themselves with blanket surveillance of the whole population. Without permission or debate or scrutiny or safeguards.
I thought the campaigner and journalist Henry Porter hit the nail precisely on the head this morning when he asked why it was that no political party has complained, and that the public seems so uninterested that their correspondence is being read. The Today programme failed even to report the story in their early bulletins, for goodness sake, which is both bizarre and rather pathetic.
This matters, not so much because privacy matters (though it does), or because the surveillance organised by the Stasi mattered (though it did too, see picture), but because this kind of apparatus always misunderstands threats. Because it multiplies the besetting sin of the security world many times over.
Fine if they ignore you, but just occasionally they don't - and they then fling these individuals, guilty and innocent, into a nightmare Kafkaesque world where there seems to be no escape.
Because I am a sad type of Liberal, addicted to history, I keep asking myself what Mr Gladstone would say.
I suspect he would recognise that total surveillance must occasionally provide useful clues and leads. But he would complain about un-English, Napoleonic, 'continental' forms of tyranny.
He would also complain about the expense - and when 850,000 people are security cleared for this kind of activity in the USA alone (more than half the number employed by the NHS), then it must cost vast sums, paid for by taxpayers.
Finally, he would complain about the threat to business. Because when you create a 'backdoor' into the emails of every business in the world, and you give 850,000 people access to it, then it will mean that they will inevitably be read elsewhere too - it means no business can be private.
And when privacy and business security is impossible, and the foreign agencies representing foreign competitors (should I mention the Chinese here?) can read everything, then business becomes impossible.
This is the Liberal issue of our times. It matters in the same way that illegal snooping by newspapers matter (see Chris Huhne's excellent article on that this evening). In the great balance of things, it certainly doesn't make me any safer.
How do I know? Because Mr Gladstone told me...