Clear winner: The Regent Palace.

Right on Picadilly Circus in London. Total dump. I was on a very tight budget with three friends several years ago. We got a triple room for one night. Puke from drunk guests in the community bathrooms. The smell in the halls was either industrial strength cleaner or beer/vomit, etc. depending on the time of day or night.

And, when it came time for us to draw straws to see which one of us was going to sleep on the floor...