I remember Carlsberg Spesh and Tennents Super (not sure I spelled those right) being the super strength beers when I was in the UK. Tennents Super tasted a bit like vegemite, I thought, which isn't surprising because (as I found out later) they are both made from the same stuff - the yeasty sludge leftover after making beer.
I remember that they were talking about raising the tax on it. I knew a couple of guys who got drunk on it once and swore off the stuff for life.