An Act was passed in 1790 for inclosing (or enclosing using the modern term) the common fields of Polebrook, then reported to contain about 1,400 acres.
This act created legal property rights to land that was previously considered common.
There is more details here.
See ‘A Historical Outline of Land Ownership in England‘
This is how it was reported in the House of Lords Journal
Polebrook Enclosure BillThe Lord Bishop of Bangor reported from the Lords Committees, to whom the Bill, intituled, “An Act for dividing and enclosing the Common and Open Fields, Meadows, Commonable Lands, and Waste Grounds, in the Parish of Polebrook, in the County ofNorthampton,” was committed: “That they had considered the said Bill, and examined the Allegations thereof, which were found to be true; that the Parties concerned had given their Consents to the Satisfaction of the Committee; and that the Committee had gone through the Bill, and directed him to report the same to the House, without any Amendment.”