Fresh roasted Ethiopian coffee
I just had the best cup of coffee I have ever had, in my life at http://www.stjohnswaterloo.org/ . It was so smooth and tasteful. I watched the guy roast the beans on a charcoal burner, while he waited for customers. Unbelievable. I had an espresso or americano, I don't really remember. It cost 2 pounds, and was a whole meal just by itself. There was other food there, kind of a food court in the area around the entrance of the chapel. It is right across the street from Waterloo station. If you ever drink commercial coffee again - shame on you. If you come to London and don't visit this guy - shame on you.
One of the best experiences possible.