Britain's Lieuteunent General Frederick E. Morgan had been appointed to develop the Case C of the Operation Rankin. The Operation Rankin was the plan for a suddenly fall of the enemy. The "Case A dealt with the sitation in which the Germans might become so weak that only a miniature Overlord" invasion might be necessary, Case B conceived a strategic withdraw from some parts of the occupied countries while still leaving the bulk of their forces along the European coastline to repel an invasion; and Case C dealt with a sudden German collapse either before, during or after the actual invasion itself.
Morgan was bothered by Berlin, foresseing that the division should follow an equal tripartite force.
As for the British and American zones, their north-south relatioship seemed to Morgan to have been predetermined by one seemingly ridiculous but relevant fact: the location of the British and American bases and depot back in England""The Americans always on the right, and the British always on the left, facing the continent."
"I do not believe," Morgan said later, "that anyone at the time could have realized that the full and ultimate implications of the quartering decision - which in all probability was made by some minor official in the War Office. But from it flowed all the rest."
C. R. The last battle. 1966.