We seem to have drifted a long way from my original point, that these closures are extremely bad for our tourist industry.
As regards what hotel scanners can detect (if they are switched on) and what perimeter one should close, I suspect we are all a little out of our depth. The Sheraton is not a very secure place because it was never intended as a high security installation. Its a hotel ! Any building that is so prominent and visible from such a great distances constitutes an unnecessary risk. You know you can get a stinger missile on ebay now.
My 3 previous posting before Doha were Thailand, Sri Lanka and Pakistan, all places witha REAL security problem. Notwithstanding I never saw a major hotel closed in any of those countries.