Flame is a mysterious and marvellous thing. Apparently, bar-be-cuing is making a comeback. Either way, an expert friend of mine, a professor who happens to also be a vet, a beef farmer and an expert chef, told me that it was unwise to trust any food provider who offered burgers "medium" or worse, "medium rare". All burgers should be "well done", anything less is potentially dangerous. A little tip, that.