For the exercise we are required to take three pictures with a single point in a different part of the frame. I have drawn lines on each image to show the graphic relationship the point has to the frame. Each image has the point off centre toward the edge of the frame. I have also converted all images to either black and white or monochrome so colour does not distract or become a contribution to the picture.
This night time image of St Paul's is deliberately very dark so the light around the cathedral enhances the focus of the viewer. The darkness all around adds as it shows that the picture was taken from a high point. If it was cropped to just the cathedral I could have been standing anywhere. This is clearly a roof top picture where you focus on the dome of St Paul's.
Trying to take a picture with a single point along the Thames proved to be very challenging. The river is just too busy. I had dozens of points. So I asked these seagulls to help me out. Please stand apart and still for 10 minutes. I have used an aperture of 5.6 and focused on the gull. placed toward the bottom on the right with tall buildings and skyline in the other two thirds of the frame gives a sense of the gull having just flown in and landing on the wall. Or alternatively about to fly into this part of the frame.
The sign and safety buoy placed in the bottom third of the image gives the sense of somewhere to throw the ring should it be needed. The empty water gives the No Bathing sign some authority.