Introduction: In 2020, the UK Health Security Agency (UKHSA) established a large-scale testing programme to rapidly identify individuals in England who were infected with SARS-CoV-2 and had COVID-19. This comprised part of the UK government′s COVID-19 response strategy, to protect those at risk of severe COVID-19 disease and death and to reduce the burden on the health system. To assess the success of this approach, UKHSA commissioned an independent evaluation of the activities delivered by the NHS testing programme in England. The primary purpose of this evaluation is to capture key learnings from the rollout of testing to different target populations via various testing services between October 2020 and March 2022 and to use these insights to formulate recommendations for future pandemic preparedness strategy. Methods and analysis: The proposed study involves a stepwise mixed-methods approach, aligned with established methods for the evaluation of complex interventions in health, with retrospective and prospective components. A bottom-up approach will be taken, focusing on each of nine population-specific service settings. We will use a Theory of Change to understand the causal pathways and intended and unintended outcomes of each service, also exploring the effect of context on each individual service setting′s intended outcomes. Subsequently, the insights gained will be synthesised to identify process and outcome indicators to evaluate how the combined aims of the testing programme were achieved. A forward-looking, prospective component of this work will aim to inform testing strategy in preparation for future pandemics, through a participatory modelling simulation and policy analysis exercise. Disclaimer: This is a provisional draft protocol that represents research in progress. This research was commissioned and funded by UKHSA, to be performed between August 2022 and March 2023. The scope and depth of testing services and channels covered by this research were pre-agreed with UKHSA and are limited to the availability and provision of data available at the time this protocol was written.