Take 4 photographs which use diagonals strongly.
I took this picture in my local park on an overcast day, hence the featureless sky. Though it provides a plain background and contrasts with the fence.
This was taken in Hyde Park and I had to wait for all of the posts to be occupied!
This image is of the shadows cast by some railings in Hyde Park.
What have I learned?
As stated in the notes, I found it alot easier to show diagonal lines than vertical or horizontal. Although horizontal and vertical lines are prevalent in many structures, it was difficult to try to be creative and avoid lines that are staring you right in the face.