As I was taken my photos of Blackfriars bridge, I noticed the red bus approaching. It occurred to me that the bus and the cranes matched and provided a contrast to the colour of the bridge and the pillars of the old railway bridge. So, I de-saturated all colours apart from red.
The lamposts, scarf and buoy (can you spot them?) add to the effect – even if I didn’t notice them as I took the image!