Theme Day - out of focus

This month's theme for the City Daily Photo community is out of focus.  For me having something out of focus needs to have a purpose.  In my contribution to the theme day, I have used a slower shutter speed to make the people blurry to give a sense of how frenetic and busy London's underground can be.  The stairwell remains sharp so it is obvious the movement is deliberate and not a mistake.  See how others have interpreted the brief here.