If you go Back To Square One then you go back to the beginning. The phrase can be traced to the 1930s when commentary on football matches began to be broadcast by the BBC. The Radio Times, the BBC's scheduling magazine, introduced a numbered grid system that they published enabling commentators to indicate to listeners exactly where the ball was on the pitch. Square one was the goalkeeper's area and so, whenever the ball was passed back to him, play was referred to as being "back to square one".