Big Ben and houses of parliament Depth of Field being used creatively - I feel this gives a much better effect than having shot the image with a smaller aperture which would give a bigger focus in the image (so Big Ben in the background would have been in focus too).
Shutter Speed: A Beginner's Guide... I've always believed that in photography, you should avoid getting bogged down in the technical side of your hobby, and focus on developing your creative talent. However, there are certain technical elements that are essential to getting a good photo - shutter speed is one of them
“In a world addicted to speed, I blur the moments into one unholy smear. ... When I fully enter time’s swift current, enter into the current moment with the weight of all my attention, I slow the torrent with the weight of me all here.” ― Ann Voskamp, One Thousand Gifts: A Dare to Live Fully Right Where You Are