The unofficial derivation of "sod off"

David Roberts wrote, about the idiom "sod off":

Just occurred to me that perhaps you wanted to know the origin of this popular phrase. It all started back in the Middle Ages with the turf-dwellers of Romford. These hard working peasant folk lived in low grass covered houses on the banks of the Thames. In order to enter or leave one of these Squatts as they were known, a piece of turf or sod would be lifted away from the door opening. The term "sod off" was thus coined to mean "The door is open, feel free to leave". This term eventually replaced such phrases as "Well, don't let me keep you", "My, is that the time?" and "We must have lunch together one day". Interestingly the term "sodding" was often used to refer to unwelcome guests due to the work of lifting the sod to see who's there. This is still in common use today as in "Oh bugger, it's the sodding Jehovah's Witnesses". If you are very interested you could find a copy of "England as it is spoke" by Queen Victoria's brother Albert, written shortly before he was eaten by the lion.