The common wasn't for pleasure- it was common grazing ground- sometimes used for fairs.
Common grazing ground used for fairs, but I thoght that even in this period they were also used for other leasure purposes (archery practice and other sports, for instance).
It may well have been allocated to the parsonage as recompense for the reduction in tithes caused by enclosure,(not to keep it out of the landowner's hands) and for Northampton, eighteenth century enclosure as opposed to sixteenth or other century enclosure is highly likely.
That was certainly just a guess. I have no real idea how ownership of these grounds went south of the border.
Keith