We generate vast amounts of data concerning our health, movements, and habits when interacting with technology and digital services. These digital traces are a vital key to solving society's biggest problems-for example, electronic health records can support cancer surveillance efforts, and mobile location data can support humanitarian action for disaster relief. While privacy researchers have proposed numerous techniques to safely collect, analyse, and share personal data, these systems are not without their limits. Indeed, a number of supposedly anonymous datasets have been re-identified, and a lack of public confidence derailed the NHS's care.data and GP data collection scheme that tried to share de-identified health data for research. To address the privacy threats involved in releasing sensitive human data, regulators have advocated for use of modern privacy-enhancing technologies (PETs) that have stronger privacy guarantees. However, some PET techniques-such as injecting noise into the data, or creating 'synthetic' datasets-can fundamentally distort data in unknown but potentially harmful ways, for example if rare diseases are suppressed from synthetic data, or vulnerable communities are further marginalised. A group of 50 US academics led by Prof. Gary King recently warned the US Census Bureau that the secrecy of anonymisation techniques can lead to "biases that have never been publicly quantified". This lack of understanding of how PETs will impact research and data analysis-and the policy interventions that rely on it-complicates recent calls to "unlock the power of data" for the public good. Over the course of this Fellowship, I will provide a pathway to guarantee both the privacy of data subjects *and* the utility and integrity of research data. My proposal pioneers a statistical learning and computational approach to guide the development of fair and usable PETs, allowing regulators and civil society-for the first time-to make evidence-based determinations for which privacy mechanisms to use when collecting and releasing sensitive datasets, and researchers to independently audit the validity and integrity of any anonymised data they receive. It will pioneer computationally-heavy replication studies to understand how PETs can cause harm (WP1); statistical methods to help PET developers 'extrapolate' guarantees from lab studies to the real world (WP2); technical standards and certification to quantify the impact of PETs (WP3); will produce online tools to allow researchers to audit deployed PETs (WP4); and undertake a broad programme of outreach and engagement to inform practice in policy, industry and academia (WP5). The Fellowship will thereby provide a framework to make research using digital traces safe and reliable; support data-driven policy interventions that rely on anonymised administrative data; and inform the regulation of underlying AI technologies-such as generative AI for synthetic data.

The UK Longitudinal Linkage Collaboration (UK LLC) has been set up to bring together data from longitudinal study participants with their routine records. This is done in a secure way to help researchers work to improve health and wellbeing throughout and beyond the COVID-19 pandemic. What does this mean and why is it important? Longitudinal studies gather data about people's lives over time. This data can lead to discoveries that improve people's lives. Linking study data with health and administrative records will help researchers deliver public benefit research. Continued funding of UK LLC will allow us to use what we learned from the pandemic and offer the resource as a long-term service for UK longitudinal research. It will make possible research into our biggest health/socio-economic challenges and widening health inequalities. The large scale, diverse linked data will provide the numbers for researchers to study rarer outcomes and harder-to-reach populations. How does UK LLC work and how is it unique? UK LLC will support a national move to standardise and regulate data access for all Longitudinal Population Studies (LPS). We are a national Trusted Research Environment (TRE) for longitudinal research. A TRE is a secure computer system that allows researchers to analyse data from within the environment. Our TRE holds data from 280,000 study participants from across the UK. The data itself is held within the TRE - it never leaves, and it's never sold on. Data is linked to regularly refreshed NHS and environmental records (eg, air pollution, noise pollution). We have secured approvals to link to employment, earnings, benefits and education records from the UK Government organisations who own this data. We are working with studies to make sure participants are aware of this use of their data and can discuss any concerns with their study team. We know that some studies may choose not to permit all linkage options. This new resource has been made possible by providing an easy and consistent way for studies to join and by centralising our operations. Our processes were built from the ground up with particular focus on safeguards and security. Who is involved in UK LLC? Our partnership includes UK LLC, lead researchers from 24 studies and many other key individuals and organisations working with health data. We will support parts of the UKRI Population Research UK (PRUK) vision to centralise support for studies. This will unlock new scientific opportunities. We have public contributors, including study participants, who form an important part of our existing and planned activities. They focus on representing the views of publics and study participants, working to make sure the way we talk and promote the resource is transparent, clear and demonstrates the public benefit. What will this funding allow UK LLC to do? It will allow us to continue to offer this valuable national resource for research and to make it better. It will enable UK-wide analyses, allowing research results and effects on policies to be measured and compared. We will quickly be able to bring on new and existing study data. As researchers use the resource, it will create an ever-increasing knowledge base to build and improve on. Importantly, we will be able to learn from the coronavirus pandemic and use the TRE to support a quick response to future crises and NHS/UK Government needs. Continued funding will deliver our three core objectives to a) make UK LLC a globally unique resource in the breadth and depth of its capability, b) provide a route for studies to move to working with their data in TREs and c) empower researchers to get the best out of the available data and continue to build and grow its capacity and improve its quality as a high value research resource for the UK. By bringing this data together, we're providing a way for research to meet the needs of people across all our communities.