We were staying in the (excellent) hotel "the Tower", located adjacent to the Tower Bridge. For a few hours we even had a room with a view towards the bridge! This view was drawn and painted from the 1st floor bar, while resting our tired feet and enjoying a nice pint of Guinness.
I should add that I drew this image late in the evening. As the bridge was fully lighted I was able to draw it as if it was daylight. I considered drawing it as if by night, but the bar was dimly lit and you need good light to paint an acceptable night scene. Believe me, I tried.