Sod's Law is just a variant on Murphy's law which is usually stated briefly as: "If anything can go wrong it will." In 1949 at Edwards Air Force Base in California, the development engineer, Captain Edward A Murphy Jr - who gave his name to the concept - actually stated it as: "If there are two or more ways to do something, one of which can result in catastrophe, someone will do it."
There is, however, a version of the same idea in German from much earlier times. It reads: "Alle Kunst ist umsonst Wenn ein Engel auf das Z�ndloch brunzt", which translates as: "All endeavour is in vain when an angel pees in the touch-hole of your musket"!