In Lambeth LBC v SoS for CLG (2018) EWCA Civ 844 considered again the interpretation of planning permissions (paragraphs 23-37) and implication (paragraphs 63-75). Lewison LJ (with whom Hamblen and Coulson LJJ agreed) said as to the interpretation of a condition that the ultimate question was what a reasonable reader would understand the words to mean when reading the condition in the context of the other conditions and of the consent as a whole. This is an objective exercise in which the Court will have regard to the natural and ordinary meaning of the relevant words, the overall purpose of the consent, any other conditions which cast light on the purpose of the relevant words, and common sense. It is not right to regard the process of interpreting a planning permission as differing materially from that appropriate to other legal documents.
As to implication of words into a condition, this is possible, but great restraint will be exercised in doing so. The limited range of available extrinsic evidence is a critical factor. In the case of a private contract, recourse to the background facts may be the reason why a term is implied. That is not possible in a public document. However, even in the case of a public document a term may be implied where that term is intrinsic in the language of the document itself. In the sphere of private contracts it is now established that there are, in essence, two routes to the implication of a term. Either the term must be necessary to give business efficacy to the contract; or it must be so obvious that it goes without saying. “Business efficacy” will not be achieved if, without the implied term, the contract would lack commercial or practical coherence. It is to be noticed that in this context the relevant purpose is the purpose of the contract: not simply the purpose of one of the contracting parties. Given the public and permanent nature of a planning permission it is not easy to see how these tests can be directly applied without some modification. No new condition should be implied unless the reason for the condition is apparent from the planning permission itself.