Triplecheck?
I just came back from BAH, an airport I use frequently and their security, tight before, is now even tighter. I'm no expert on the efficacy of profiling passengers, but the mantra in BAH seems to be "make them think twice".
Before check-in all your bags are X-rayed while you watch. Hold luggage is then sealed with nylon tape. You then get a frisk and metal detector run over you. Off to check-in. Next up going airside. Once more your cabin bags are X-rayed and you pass through the standard machinery with more frisking/detecting if you go beep (I always do!). Finally after the gate, more random bag searches and frisks/detectors on the airbridge.
Now I know this is never going to be practical at a large airport such as LHR, but if you had any ulterior motive in mind, then I would suggest that BAH would not be one of your chosen starting points.
Contrast that with an experience at ORA late last September when I'd left some sunglasses at check-in. I went up to the barrier to see if someone could help, stood patiently "excuse me'ing" for a couple of minutes whilst the guard chatted to his buddy (with his back to me) then thought "sod it" and walked through. Fetched my glasses and came back airside.
My take on this is that in some airports people have a job to do, and do it well with the co-operation of passengers. In other airports people just view it as something to do to idle away the time between 9-to-5. Unless or until you get rid of that mentality, you will always have alarming differences in the effectiveness of the security checks.