Hallam Land Management Ltd v Secretary of State for Communities and Local Government and Eastleigh Borough Council [2018] EWCA Civ 1808

How precisely must the decision maker determine the housing shortfall, especially if there is disagreement:

“48. Relevant authority in this court, and at first instance, does not support the proposition that, for the purposes of the appropriate balancing exercise under the policy in paragraph 14 of the NPPF, the decision-maker’s weighting of restrictive local plan policies, or of the proposal’s conflict with such policies, will always require an exact quantification of the shortfall in the supply of housing land. This is not surprising. If the court had ever said there was such a requirement, it would have been reading into the NPPF more than the Government has chosen to put there, and more than is necessarily implied in the policies it contains.

1. …[T]hree main points emerge….
2. First, the relationship between housing need and housing supply in planning decision-making is ultimately a matter of planning judgment, exercised in the light of the material presented to the decision-maker, and in accordance with the policies in paragraphs 47 and 49 of the NPPF and the corresponding guidance in the Planning Practice Guidance (“the PPG”). The Government has chosen to express its policy in the way that it has – sometimes broadly, sometimes with more elaboration, sometimes with the aid of definitions or footnotes, sometimes not. …It is not the role of the court to add to or refine the policies of the NPPF, but only to interpret them when called upon to do so, to supervise their application within the constraints of lawfulness, and thus to ensure that unlawfully taken decisions do not survive challenge.
3. Secondly, the policies in paragraphs 14 and 49 of the NPPF do not specify the weight to be given to the benefit, in a particular proposal, of reducing or overcoming a shortfall against the requirement for a five-year supply of housing land. This is a matter for the decision-maker’s planning judgment, and the court will not interfere with that planning judgment except on public law grounds. But the weight given to the benefits of new housing development in an area where a shortfall in housing land supply has arisen is likely to depend on factors such as the broad magnitude of the shortfall, how long it is likely to persist, what the local planning authority is doing to reduce it, and how much of it the development will meet.
4. Thirdly, the NPPF does not stipulate the degree of precision required in calculating the supply of housing land when an application or appeal is being determined. This too is left to the decision-maker. It will not be the same in every case. The parties will sometimes be able to agree whether or not there is a five-year supply, and if there is a shortfall, what that shortfall actually is. Often there will be disagreement, which the decision-maker will have to resolve with as much certainty as the decision requires. In some cases the parties will not be able to agree whether there is a shortfall. And in others it will be agreed that a shortfall exists, but its extent will be in dispute. Typically, however, the question for the decision-maker will not be simply whether or not a five-year supply of housing land has been demonstrated. If there is a shortfall, he will generally have to gauge, at least in broad terms, how large it is. No hard and fast rule applies. But it seems implicit in the policies in paragraphs 47, 49 and 14 of the NPPF that the decision-maker, doing the best he can with the material before him, must be able to judge what weight should be given both to the benefits of housing development that will reduce a shortfall in the five-year supply and to any conflict with relevant “non-housing policies” in the development plan that impede the supply. Otherwise, he will not be able to perform the task referred to by Lord Carnwath in Hopkins Homes Ltd. . It is for this reason that he will normally have to identify at least the broad magnitude of any shortfall in the supply of housing land.”

However: (para 18) “…In these circumstances Lindblom LJ concluded that the Secretary of State’s reasons in Hallam were in this respect deficient, because the developer was entitled to know how and why the Secretary of State had reached his assessment of the shortfall in the light of the inspectors’ assessments to which he had been referred and which he expressly stated had been fully considered. The Secretary of State’s decision accordingly fell to be quashed.”