In R (Manchester Ship Canal Co) v. Environment Agency  EWHC 1643 (Admin), Lang J considered the Environment Agency’s policy approach to mapping the “undefended scenario” flood zones on the national Flood Map. Taking the precautionary approach required by former PPS25, the Agency had treated several sets of sluice gates on the Manchester Ship Canal as “formal defences” that were assumed to fail in flood conditions, placing much of the development land adjoining the Canal in Flood Zone 3. Lang J held that following the Supreme Court decision in Tesco Stores v. Dundee City Council  UKSC 13 , the meaning of the Agency’s policies on classification of flood defences was a question of law for the court. The Agency had misinterpreted its policies and its decision was quashed. Gordon Nardell QC and Christiaan Zwart appeared for the Agency.