I'm not sure when burgers got so popular in the UK. When I was younger they were cheap, squashy but strangely delicious things you had in McDonald's as an end-of-term treat (until BSE happened, anyway). At some point they must have started turning up on pub menus and now there are whole websites devoted to them and several chains claiming to produce the 'best burger in town' at a price that would have bought at least half a dozen Happy Meals in the early 90s.