In response to the UK National Data Library: Technical White Paper Challenge put forward by Wellcome and the Economic and Social Research Council (ESRC), HDR UK submitted a white paper outlining a technical vision and architecture that could be adopted by a future National Data Library, for the benefit of the research community and the UK population. In this paper we describe the National Data Library as a secure, distributed ecosystem of environments that should – in the context of health and health-relevant data – unite the UK’s diverse health and social care datasets. Its core objectives as they pertain to health data should be to: Accelerate health research: Enable secure, equitable access to data for researchers, policymakers, and innovators. Transform the NHS: Support personalised medicine, operational efficiency, and health equity through data-driven insights. Drive economic growth and attract global industry to the UK: Strengthen the life sciences sectorby fostering innovation in AI, digital health, and therapeutics. Promote and enable industry: through common, standardised collaborative communicationbetween services, enabling the exchange of data, analysis workloads and other information across secured cloud networks, with accessible standards and with minimal restrictions on the implementing software. Align with international frameworks: such as the European Health Data Space (EHDS) to enableglobal collaboration and maintain the UK’s leadership in health data innovation. To understand the social/environmental determinants to health: supporting the quest to pivotfrom "sickness to prevention". This white paper focuses on principles and best practice the NDL should consider in assembling the necessary data architecture for future health data research. The associated DARE UK white paper provides an infrastructure-architectural view across all data domains.