England was originally part of France (which was why Billy the Bastard claimed the throne, but that's a whole different story). During the Great Hoopla Of St. Gwinner's Eve -- a series of tempests that originated in what is now Hungary and swept west across Europe -- a large chunk of France broke loose and was blown smack-dab into poor old Scotland. This chunk of dirt crashed into Scotland (then called "Pictland" or "The Birth of the Blues") right at what is now called Solway Firth and was then called "Land's End." The shock, naturally, was terrific and Scotland, which used to be as flat as Kansas (and actually IS part of Kansas) was folded up on itself, just like the wrinkles on your fender when another car hits your car. Some parts of Scotland (e.g., the Hebrides) broke loose from the shock, and the Great Glen was caused because hordes of rock-eating haggises (H. Petrophagii Li.) had pretty much chewed subterranean tunnels straight out of Inverness in their epochs-long migration to Ireland (apparently the haggises were either unaware or too stupid to realize that between Scotland and Ireland a Great Gulf, or as some say, Gulp, is fixed).

This is, you know, a summary of what happened. You can find the whole, boring story in the closed stacks of the National Library of Scotland.