After more than a year of working at the client's I have unconsciously learnt their mannerisms.
Was just at the pantry filling up the thermos when I realised Mr Abadi coming in to fill his water tumbler, so I greeted him. My back was facing him, and I didn't turn to look around.
He was naturally surprised that I recognised him, thinking perhaps it may have been the footsteps that gave him away.
So he asked how I knew. I said it was my 6th sense.
What he didn't know was that the orange panel behind the water dispenser was glossy enough to act as a reflector. It's definitely not a mirror, but it reflects enough light just to show the silhouette of anyone who walks past it.
I just get a kick out of seeing people's reaction when I greet them without even turning to see their face.
So don't tell them our little secret ;)