I took this picture from the top of a moving bus. It was late evening, when there was just enough light to make this picture possible. It was a open-top double-decker bus belonging to the "London-by-night" tour. If you are visiting London, I would strongly recommend you to do this tour on your first evening, because it would familiarise you with all the sights of central london.

When we turned onto the road from a side street, I noticed that we would be passing under this tree. I quickly increased the ISO to 1600 and put the camera to Shutter Priority at 1/20s. By trial and error, i have found out that 1/20s usually works at dusk. The light on the tree was from a street light.