2023-2025, Sea Mammal Research Unit Consulting (SMRU Consulting), Hornsea Project Two, Improving cetacean Density Estimation from Digital Aerial Surveys (IDEAS) series https://portal.medin.org.uk/portal/start.php?tpc=015_fadf44cb-3fed-41b7-89e8-a41cb2a83290 This Final Report documents the activities undertaken towards executing the Plan for Marine Mammal Monitoring required under condition 8 (2)(h) of the Hornsea Project Two Offshore Wind Farm (Hornsea Project Two) deemed Marine Licences (dMLs). Agreement on the nature of these monitoring activities and their fulfilment of relevant dML conditions was reached in April 2020 with the Marine Management Organisation (MMO), in consultation with Natural England. It is noted that the Hornsea Project Two Plan for Marine Mammal Monitoring was focused on providing a strategic post-construction analysis of existing data to address uncertainties inherent with marine mammal monitoring data collection. The Plan did not include pre-construction or site-specific monitoring. SMRU Consulting were contracted by Ørsted to deliver a project to satisfy Hornsea Project Twos Plan for Marine Mammal Monitoring. This commenced with a scoping phase to identify appropriate datasets, develop an approach to addressing the objectives of the plan, specify deliverables, develop a budget and timeline, and form a Project Review Group (PRG). The scoping phase culminated in a detailed Scope of Work (SoW) document, finalised in January 2022. The project subsequently commenced in May 2022 with the title “Improving cetacean Density Estimation from digital Aerial Surveys” (IDEAS) and this Final Report represents the primary output from the IDEAS project. 20250901 20250321