Provided also, that the power of leasing hereby given shall not in any case extend to, or be understood to comprehend, a power of leasing, or setting in tack, the manor-place, office-houses, gardens, orchards, or inclosures adjacent to the manor-place, which have usually been in the natural possession of the proprietor, or have not been usually let for a longer term than seven years, when the heir in possession was of lawful age; and that no lease of lands shall be granted, under the authority of this Act for the purpose of building villages or houses within three hundred yards of the manor-place in the natural possession of the proprietor.