CNN: Derek is compiling a survival guide on how to cope after the total collapse of society. It is, as you can imagine, a big job. Already he has 58.8 gigabytes of material stored on his computer, he tells me impressively. Derek (this is not his real name — he says he doesn’t want me to use his real name "for obvious reasons" that he never gets round to explaining) considers himself a survivalist. The survivalist movement grew up in America in the 1960s. Encouraged …