The Romans are also credited with bringing land snails to the UK (as food). Only the slugs are native. I was told years ago by my biology teacher that if you have snails with shells in the vicinity, then it's a sure sign that a Roman settlement was nearby, as snails only move slowly and are pretty much where the Romans left them 1700 yrs ago! Don't know if that still holds good but there is some sort of logic about it. Wouldn't fancy eating them myself, even with garlic, but they don't half make a meal out of my lettuces!! So thanks, Romans....