For those of you that live in the UK, I'm sure you cannot help but be astonished at just how popular the phrase Keep Calm and Carry On has become. From nowhere it seems this design has appeared on mugs, posters, t-shirts, tea towels...You name it. Copied, evolved and parodied, it is everywhere. But where did it all begin? Watch the following video to see how the slowest viral in history came about.