Funny story - I had to go to Cheltnam on business a couple of years ago, and while I was there I was getting banner ads trying to recruit me to GCHQ. I'm guessing their staffing people don't have access to the whole file, because they were trying to recruit a foreign national with no security clearance for a job that pays 1/3 of what they're already making.
A single 1TB thumb drive could easily hold hundreds of flags for every human on the planet. Actual foreign keys, not so many ... but I'm pretty sure all of the places mentioned above have fancier infra than a single pluggable mail order drive.
Compare the Stasi's reach, with only typewriter & notch card level automation.