I tend to "Fracture" time. The plot goes up until some defining point in History, where the plot takes a very different course of action compared to real time. Like... Cuban Missle Crisis. I had a campaign that based around the idea that the Missles actually fired.
Much the course I take. I intend to do something similar in my Servants of the Queen Elizabethean FantasyCraft spy game. I am not yet certain where the fracture will be, only that it will be sometime before the Spanish Armada. (How could I not
give my players a chance to muck around with that?)
Oddly enough I have a strange urge to create an NPC by the name of Blackadder. He's very bad indeed.
The Auld Grump