Southern Water has 13 No. operational Wastewater Treatment Works (WwTWs) with Total Nitrogen (TN) permits of 15 mg/l or tighter. These works account for 23% of Southern Water total PE. Type of treatment for TN removal varies from denitrifying sand filters on trickling filter works to Modified Ludzack–Ettinger (MLE) or 4-stage Bardenpho for activated sludge processes. Pagham WwTW is a 12,000 PE works with the greatest number of WINEP drivers to be delivered in AMP7. These included the provision of additional storm storage, 60% increase in flow to full treatment, tightening of ammonia limit to 2.5 mg/l, a new total phosphorus (TP) limit of 0.25 mg/l TP and introduction of TN emission standard of 15 mg/l. This created both a significant technical challenge and an opportunity to modernise the ageing trickling filter process, which had reached its hydraulic and treatment capacity. The solution was a contemporary MLE activated sludge plant without carbon dosing designed to treat higher flows while delivering enhanced nutrient removal. Operational flexibility was embedded in the design to ensure robust performance under highly variable influent conditions caused by seasonal holiday population surges and this was compounded by the unexpected loss of a major trade effluent contributor ahead of commissioning. Key design features included multiple ferric dosing points to optimise phosphorus removal and the capability to divert crude sewage directly to the aeration lanes to enhance denitrification when required. Achieving low TP limit was also limited by the need to have sufficient phosphorus available as a nutrient for denitrifiers to meet TN standard. The flexibility in the design of nutrient removal MLE proved invaluable during commissioning, enabling the team to fine tune process conditions, respond effectively to influent variability, and progressively align plant performance with the stringent new permit requirements. The project demonstrated that intelligent process design, combined with adaptable operational strategies can future proof wastewater treatment assets, and maintain compliance with multiple WIMEP drivers during seasonal and variable influent conditions. The presentation will take the attendees through the optioneering, design, commissioning, and lessons learned from delivering the full scale upgrade of the WwTW. The presentation will also provide insight on the performance results, showing the new processes have significantly reducing nutrient load entering the Pagham Rife.