I think if you saw that image alone, without any understanding of previous images, and the way PR seeks to manipulate perceptions through the creation of essentially false and staged images, that would be a reasonable reaction.
But we all know, don't we, that the picture is posed with the specific intent of conveying gravitas, statesmanship and the like.
The reason there are now many thousands of pisstaking sendups of the picture circulating the internet is because the staging is so transparent, so blatant, and so unsuccessful, as to make it an object of derision.
Here's another where they screwed up quite badly. You'd think as a former PR person, Cameron would realise how shockingly poor these efforts are. Or perhaps that's the standard he worked to in that job, as well as his present one.
I'm sure Peter, but I was admiring the Psychological take on it.