Pigot v The Environment Agency

Section 10(1) of the Salmon and Freshwater Fisheries Act 1975 permits a fish pass to be constructed and maintained only where it causes no tangible, material injury to the milling power then exploited, or capable of being exploited, by an existing mill or turbine. The statutory limitation applies to keeping the pass in place and operational. If the pass was lawful when constructed, a later replacement of the turbine does not retrospectively remove the statutory authority to operate it. Statutory duties to conserve aquatic fauna and maintain fisheries cannot authorise conduct outside the statutory power.

Sir George Pigot owned a property on the River Kennet with a dam, sluices and turbine. The Environment Agency constructed a fish pass in 1999 under section 10(1) of the Salmon and Freshwater Fisheries Act 1975. The original Francis turbine was not materially affected. After Sir George replaced it with a more powerful Archimedes turbine, operation of the fish pass during low-water conditions reduced the turbine’s output.

The High Court rejected a claim for breach of statutory duty but otherwise granted declarations in Sir George’s favour. In [2020] EWHC 930 (Ch), the Environment Agency appealed on statutory authority and on whether the relevant milling power was assessed at construction or from time to time. The central issue was the proper construction of section 10(1).

1. The appeal was allowed on Ground 2. The High Court’s declarations were replaced by suitable declarations reflecting the Court of Appeal’s construction of section 10(1).
2. A riparian owner has rights to use the natural flow of a river and to receive it in its natural state. Material interference with those rights may constitute nuisance without proof of damage. The unappealed first-instance conclusion that the fish pass caused prima facie nuisance at low water was not disturbed.
3. The word injury in section 10(1) requires a tangible injury which is more than minimal and inconsequential. The provision does not prohibit every diminution in flow, since that would make the statutory power to construct fish passes unworkable.
4. The phrase milling power refers to power actually exploited, or capable of being exploited, by an existing mill or turbine at the relevant time. It does not include speculative or likely future machinery. The Agency must therefore assess the effect of a proposed pass on the existing milling power when construction is undertaken.
5. Maintain means keeping the fish pass in place and operational. The no-injury limitation qualifies both construction and continued operation. However, where the pass caused no material injury to the existing turbine when constructed, section 10(1) authorised its continued operation even if a later replacement turbine was adversely affected.
6. The statutory-authority defence could not assist conduct outside the statutory power. The Agency could not rely on its duties under section 6 of the Environment Act 1995 to justify keeping open a pass which section 10(1) did not authorise. On the facts, however, the pass had been lawfully constructed because the Francis turbine was not affected in 1999. The later Archimedes turbine did not alter that conclusion.

1. Court of Appeal (Civil Division): Allowed the Environment Agency’s appeal on Ground 2 and replaced the High Court’s declarations.
2. High Court of Justice, Business and Property Courts of England and Wales, Property, Trusts and Probate List (ChD): In [2020] EWHC 930 (Ch), rejected the breach of statutory duty claim but otherwise granted declarations in favour of Sir George Pigot.