To be honest I think that security standards have been lowered too far since the PIRA threat 'disappeared'.
It is too easy to give away details and information about who you are and what you do. I was in during the time when you didn't wear uniform off base, checked your car and didn't carry bergans / kitbags around at train stations etc.
Yes you could ping the blokes returning on a Sunday evening at a certain London train station but an effort was made, and security was high in peoples minds.
Perhaps the military needs to go a bit higher than Black Alpha again, if it isn't already.