I had an idea that was based around the weather and the very grey, dark and looming sky over the capital. But it wasn't quite happening.
In the end this shot of the brollies in Trafalgar Square appeared in front of me, and I originally thought of the umbrella against the Big Ben clock, so I quickly threw my f-stop to f2.8 and hit the shutter button. I thought I might be able to crop it, but when I was tweaking in CameraRaw I decided the red colour pop against black and white might work. It really was this colourful too...and she was pretty. :)
Looks OK viewed large, against black if you have time :)