Such procedures are interesting to me. I have worked in central government. I won't disclose which department, needless to say security is a high priority.
Security Vetting is a must for anyone working in the building, and I presume it is the same for ATC buildings. As a result, "we" have been CTC cleared (and in the case of the government work definitely more on top of that). We could enter and exit with whatever we liked. Only un-vetted people and visitors are checked upon arrival. In that case, it is very thorough.
I do not understand why Security is made a big thing of in the media. They are a set of simple and easy to follow guidelines. The more you follow, the safer your information / premises from theft of unauthorised incursion.
Frankly, ID cards made by a serious and security concious organisation should be difficult to forge. Best of luck destroying your undisclosed ATC building, but sadly your high explosives, thick accent, henchman look with sports bag, might be a give-away to the security
Phil