Photograph: Getty ImagesThere's something wrong with this picture. Some may say there are many things. But fundamentally, we think one single item clearly doesn't fit.
It's not Mr Cameron's faux "I'm loving the open road" grin. Nor the arm-numbing stranglehold of his backpack. Neither is it the wrist-shy fit of the Conservative leaders powder blue, fleece doublet. It is none of the above.
Take a longer look. Left leg at the top of the pedal stroke. Poised to power through another pedal turn. But what's happening with its counterpart? Knee bent also? Could Mr Cameron be riding a bike which is too small? Or maybe not even his own?
There are a great many schools of thought with regard to frame fit and sizing.
A widely used approach is the LeMond Formula - a center-to-top or c-t sizing method BIKE FRAME SIZE (in cm) = Inseam (cm) x .67
Measuring from the centre of the bottom bracket to the top of the seat tube, gives the recommended size for a road bike frame. This system was originated by engineer Wilfried Hüggi, and one of Greg LeMond's cycling coaches, Cyrille Guimard.
Others might suggest simply standing over the frame of a bike, and if there was an inch or two between the top of the top tube and one's 'crown jewels', then that was the right size.
Then there's the 'KOPS' (Knee Over the Pedal Spindle) method, which employs a plumb bob.
But even taking into account the low-rider style of Mr Cameron's saddle height, he's fooling only himself.
