Appropriate assessment is a different process from environmental impact assessment, but a recent decision by the (English) Court of Appeal shows similar general legal principles apply.

The case involved nutrient neutrality in the Solent Special Protected Area. It was claimed that a planning permission granted by Fareham Borough Council for housing was unlawful, because the Council had failed to carry out a lawful appropriate assessment in part due to its application of Natural England's technical guidance note on nutrient neutrality.

Appropriate assessment:

Appropriate assessments are required where a Habitats Regulations Assessment (HRA) has concluded that a plan or project may have significant effects on a protected habitat site/conservation area. The purpose of an appropriate assessment is to enable planning authorities to eliminate adverse effects on the integrity of these protected areas.

Unlike EIA, which is carried out by the applicant, resulting in the submission of an environmental impact assessment report (EIAR) with the planning application; HRA/ AA is done by the decision-maker when deciding the application.

Precautionary approach

Appropriate assessments require a precautionary approach to be applied, including using the "best scientific knowledge in the field".

It was submitted by the claimants that the precautionary approach required the "reasonable worst case scenario" to be assessed and that in this case the Council should not have used the national average occupancy rate of 2.4 (plus a 20% precautionary buffer) in its nitrogen budget, despite it being the figure in the NE technical guidance. Their argument was that a national average is not sufficiently precautionary.

The Court dismissed this though, concluding that the “reasonable worst-case scenario” did not have to be assessed to satisfy the precautionary principle and in this instance the adoption of the national figure (plus 20% buffer) was not challenged by NE when consulted and was only one part of the overall appropriate assessment. When considered holistically, the use of this figure was not unreasonable, despite there being differing expert opinions. An appropriate assessment does not need to reach a conclusion of absolute certainty – they need to be “satisfied that there is no reasonable doubt as to the absence of adverse effects on the integrity of the site concerned”.

The status of guidance

The Court also provided a helpful reminder on the application of guidance from Statutory Consultees (such as NE):

"It should be remembered that the technical guidance note is not statute. It does not create some additional legal requirement or test. It is an advisory document, which is neither mandatory in effect nor prescriptive of a single correct procedure to be followed. It contains guidance, whose purpose is to assist competent authorities in performing their functions under the habitats legislation. It does not assert that the approach it suggests is the only means of conducting an appropriate assessment. On the contrary, it expressly acknowledges that this approach is only “a means” or “one way” of undertaking that task"

Accordingly it was not mandatory to follow precisely the methodology laid out in NE's technical guidance. As NE had not raised concerns on the Council's application of the guidance and its methodology, the Council were considered to have acted in a manner that did not amount to Wednesbury unreasonableness.


This decision is another example of the Court's not interfering with a planning authority's actions where planning judgment is involved. Where there is guidance from a statutory consultee, planning authorities are required to treat them as such – guidance – and there may be alternative methodologies that are more appropriate in the circumstances.

NE updated its advice and expanded its application to an additional 42 local authorities in March 2022. This updated guidance reflected the High Court decision in this case and now expressly supports variations from average occupancy rates. The 2022 guidance highlights the significance of local conditions in selecting occupancy figures.

To read the judgement click here


Neil Collar


Olivia Brown

Trainee Solicitor