I'm not getting into the "security" debate, but you asked:
In relation to the fluid debate, has anyone ever suggested just HOW a potential terrorist could get any kind of offensive or harmful liquid into an UNOPENED can or tin, or a bottle with a "crown" cap ? OK, I suppose a bottle with a screw cap just could be subject to tampering; but those others . . . . . Coke, Fanta, beer, etc ?
"Home brew" shops (beer, that is) sell bottle cappers, for crown caps. Cost is around $40.00 AUD (around 15 Quid for you Poms)
Not sure about the "Home canning" shops (don't know of any), but drug smugglers are forever canning opium/coke/heroin. So if the smugglers can get hold of canning equipment, then others could, too.
DIVOSH!