Wealden District Council v Secretary of State for Communities And Local Government & Ors

Under Article 6(3) of the Habitats Directive, possible cumulative effects must be considered at the screening stage as well as during any appropriate assessment. A screening threshold may exclude genuinely de minimis effects, but cannot justify ignoring separate contributions which, when aggregated, may exceed the threshold. Decision-makers may rely on expert advice, but must make further inquiry where that advice gives no coherent reason for rejecting obvious cumulative arithmetic. An assessment infected by plainly erroneous advice is unlawful and may undermine the soundness of a development plan. In a joint plan, adoption and the statutory time limit operate separately for each local planning authority.

Wealden District Council challenged under section 113 of the Planning and Compulsory Purchase Act 2004 two spatial policies in the Lewes District Local Plan Part 1 Joint Core Strategy 2010–2030. The plan had been jointly prepared and adopted by Lewes District Council and the South Downs National Park Authority.

The challenge concerned the Habitats Regulations Assessment for Ashdown Forest Special Area of Conservation. Wealden argued that projected traffic increases under the Joint Core Strategy had to be assessed cumulatively with traffic arising from the earlier Wealden Core Strategy. The central issues were whether cumulative effects had been lawfully considered, whether reliance on Natural England’s 1,000 AADT screening threshold was irrational, and what relief was available given the different adoption dates.

The claim succeeded in part. The challenge was out of time against Lewes District Council’s adoption, but in time against the South Downs National Park Authority’s adoption.

1. Under section 28(2) of the Planning and Compulsory Purchase Act 2004, the statutory regime applies to a joint plan as it applies to a single plan. Adoption therefore takes effect separately for each authority when that authority adopts the plan. Section 28(3) does not make adoption simultaneous.

2. Article 6(3) requires possible in-combination effects to be considered at the screening stage. The DMRB may be used to eliminate genuinely de minimis effects, but cannot exclude cumulative effects from consideration.

3. The 1,000 AADT threshold was a permissible screening yardstick in principle. It did not permit the decision-makers to treat a 950 AADT contribution under one plan and a 190 AADT contribution under another as separately neutral. The contributions had to be aggregated.

4. Natural England’s advice that the threshold adequately covered cumulative effects lacked a coherent empirical or logical basis on the known facts. The decision-makers should at least have made further specific inquiry. Reliance on the plainly erroneous advice infected the Habitats Regulations Assessment and constituted a Wednesbury error in the evaluative process.

5. The Inspector had considered Wealden’s representations. There was no requirement to address each representation seriatim. The error lay in the flawed assessment, not in the Inspector’s treatment of the representations as a separate ground.

6. Policies SP1 and SP2 were quashed to the extent that they formed part of the development plan for the South Downs National Park Authority’s administrative area. The court directed Natural England to reconsider its advice and ordered that the judgment be sent to Highways England for review of the DMRB.

First-instance statutory review under section 113 of the Planning and Compulsory Purchase Act 2004. The Joint Core Strategy had been examined and found sound by an Inspector, then adopted separately by Lewes District Council and the South Downs National Park Authority.