Was entering the FastTrack lane (T3) at LHR this morning. As I enter it a woman comes up to me & says do you mind if I put this on you & starts to stick a neon green sticker to my chest. I was startled & backed up a step. Excuse me? What is that? Her - it's an observation number (it said N50 btw). Me - what exactly is it for? Her - (getting the sense I wasn't thrilled about it) said it's ok if you don't want to do it. Me (politely) thank you & moved forward.

Later in the fasttrack line leading up to the magno machines saw basically every other person w/ the bright green thing stuck on their chest! There was a woman w/ a clipboard just before the conveyor, but I didn't look around to see if there were additional cameras.

So what's the observation # for, and what exactly are they observing? Anyone know about this? Just curious.

Cheers.