What is the test for a valid building scheme?

In Potts, Slatter J. discussed the requirements of a building scheme. He held at paragraph 25: The test for a valid building scheme was outlined in the decision of Parker, J. in Elliston v. Reacher, [1908] 2 Ch. 374 at 384, affirmed [1908] 2 Ch. 665: ... it must be proved (1.) that both the plaintiffs and defendants derive title under a common vendor; (2.) that previously to selling the lands to which the plaintiffs and defendants are respectively entitled the vendor laid out his estate, or a defined portion thereof (including the lands purchased by the plaintiffs and defendants respectively), for sale in lots subject to restrictions intended to be imposed on all the lots, and which, though varying in details as to particular lots, are consistent and consistent only with some general scheme of development; (3.) that these restrictions were intended by the common vendor to be and were for the benefit of all the lots intended to be sold, whether or not they were also intended to be and were for the benefit of other land retained by the vendor; and (4.) that both the plaintiffs and the defendants, or their predecessors in title, purchased their lots from the common vendor upon the footing that the restrictions subject to which the purchases were made were to enure for the benefit of the other lots included in the general scheme whether or not they were also to enure for the benefit of other lands retained by the vendors.