National government is committed to reaching net zero carbon emissions by 2050 and the Mayor of London by 2030. But achieving this will mean radical action on retrofitting London's buildings and in particular homes with effective insulation and low-carbon energy systems. National and London government have stepped up retrofitting activity and funding over the last few years, and through the Retrofit London Steering Group, all layers of London and national government are working closely together. Nevertheless, retrofitting remains a major challenge for the capital, which will not meet its net zero 2030 target or even the national 2050 target, without a step-change in the pace of retrofitting. At the same time, retrofitting at the pace and scale required represents an opportunity for London and other regions, helping lower energy costs and generating new jobs and business opportunities. We propose a partnership (London Research and Policy Partnership) to bring academic researchers, policymakers, businesses and community and voluntary sector experts together and undertake research and ideas generation that could help accelerate the retrofitting of London's housing and other buildings. We are particularly interested in how policymakers can build on existing activity and use public sector funds and other powers to unlock demand for and supply of market retrofitting services. We will approach this challenge from a 'just transition' perspective: we want to ensure that reaching net zero and retrofitting buildings is done in a way which helps 'level-up' London, lowers living costs for the poorest households and provides training and job opportunities for all Londoners, and especially those from disadvantaged backgrounds under-represented in the retrofitting sector. We will map and analyse existing retrofitting policy, funding and on-ground activity in London and assess its strengths and weaknesses and the opportunities of, and threats to, significantly escalating retrofitting. We will hold an initial workshop to identify three particularly significant challenges that are preventing the just transition to zero carbon homes and other buildings in London and then hold three additional workshops each focused on better understanding and developing solutions to these challenges. These workshops will bring together a wide range of relevant expertise, including representatives of community and voluntary sector groups. We will run them on World Café principles - an approach designed to promote open and equitable approach to group discussions. We will draw on our mapping, analysis and ideas generation to develop a theory of how retrofit could reach critical mass in London. We will develop a robust and equitable approach to stakeholder and public engagement to guide future partnership activity and identify further research and analysis, quantitative and qualitative, that could help the drive to reach critical mass in retrofitting. We will work with researchers at the School of Advanced Study to explore and identify the role that arts and humanities disciplines could play in this research. We will also set out how we will build on this collaboration to develop a broader equitable and sustainable London research, innovation and policy partnership, able to work collaboratively with other regional and national partnerships and respond to changing policy priorities. Finally, we will evaluate this work, to learn lessons for future research policy partnerships. This project will be led by the London Research and Policy Partnership (LRaPP). LRaPP was launched in July 2021 to promote joint working between policymakers and university researchers in addressing London's critical policy challenges. Lead partners include the University of London, the Greater London Authority, London Councils, University College London, and Capabilities in Academic Policy Engagement.