The national collection is distributed throughout communities, localities, and national organisations. In the past two decades communities have adopted digital technologies to gather and record their collections in a form of 'citizen history' that has created a truly democratic and vast reservoir of new knowledge about the past. This reservoir could immeasurably enrich our national and global understanding but remains largely untapped, hard to find, and at risk of disappearing altogether. The intellectual and economic investment in community-generated digital content (CGDC) is immense and its rich and diverse content is one of the UK's prime cultural assets, but it is 'critically endangered' due to technological and organisational barriers. CGDC has proved extraordinarily resistant to traditional methods of linking and integration, meaning that resources often funded and produced by the public stand alone or are inaccessible. Diverse community-focused voices, sustaining the fragile histories of communities in transition, have effectively been silenced within our shared national collection. Existing solutions to this problem involving bespoke interventionist activities are expensive, time-consuming and unsustainable at scale, whilst any unsophisticated computational integration of this data would result in a lowest-common-denominator solution which would erase the meaning and purpose of both CGDC and its creators. The Our Heritage, Our Stories project responds to this urgent challenge by bringing together a powerful partnership, including researchers in digital humanities, archives, history, linguistics, and computer science at our HEI partners, the Universities of Glasgow and Manchester, with world-leading archive and digital infrastructure development at The National Archives (TNA), the project's lead IRO. This team will bring cutting-edge approaches from cultural heritage, humanities and computer science to dissolve existing barriers and develop scalable linking and discoverability across CGDC and the collections of TNA. We will collaborate in this process with leading UK heritage organisations, including Tate, the British Museum, the National Libraries of Scotland and Wales, the National Lottery Heritage Fund, the Public Record Office of Northern Ireland, and a network of smaller regional and local heritage organisations holding digital content created by and relating to communities. Our geographic range is essential for a truly national approach which engages with every part of the UK. Our project will use multidisciplinary methods to make previously unfindable and unlinkable CGDC discoverable within the national collection, while respecting and embracing its complexity and diversity by co-designing and building sophisticated automated tools to make it searchable and connected. We will showcase its new accessibility to the world through a major new public-facing Observatory at TNA where people can access, reuse, and remix this newly integrated content. As we dissolve barriers and add meaningful links across these collections, we will make them accessible to new and diverse audiences and open them up for research - demonstrated via multidisciplinary case studies - and embed new strategies for future management of CGDC into heritage practice and training. Public engagement is a driving theme in our project, which will be developed on principles of co-production and participatory design. The lasting legacies of this project will be the wealth of previously siloed, hidden, and fragmented CGDC it will situate and render discoverable. By so doing, we will revolutionise our understanding of the past, and the methods and means to achieve this, by developing cutting-edge tools, AI methods, historical and linguistic research, and new frameworks for sustainable archival practice. By enabling CGDC to be re-used and reimagined, we will help it survive and be nourished, for the future and for our shared national collection.