It seems that every new optical illusion that crops up online claims to be trickier than the last.

But apparently only a tiny one per cent of the population will be able to spot the hidden assassin in this vintage illustration.

This image, posted to Playbuzz, features a man drawing a gun as he prepares to engage in a duel, while a group of bystanders look on - but where is his adversary?
The opponent will soon need to reveal himself so that the action can begin, but for the time being he remains invisible.

It's even more difficult to see him blending into the background because of the black and sepia toned image.

Between the two trees

I have seen him