Originally Posted by corporate-wage-slave

It is clearly signposted, but there may not be so much to the checkpoint as you enter the airport building, depends on the general security situation. Then you head towards the middle of the concourse, and the route to main security. In that central area is the queue system for HBO checks, if you have a boarding pass, and when you get to the desk then you may be asked questions. My last visit the only question was "did you pack the bag yourself?" and they waved me through before I could say "yes". But other people where asked many more questions than that. You can go to the BA desk instead, I can't think why you would do that, in which case the same security control is done in the queue zone before the BA desk. As for timing, in my case I had a 15 minute queue but it was the last flight before the Sabbath so 3 hours seems too much if anything.