This NIHR funded study is a multi-centre two-arm cluster randomised controlled trial with an embedded process and economic evaluation. Participants will be recruited from 32 homeless centres across Great Britain. The study is led by Prof Lynne Dawkins at London South Bank University and Dr Sharon Cox, University College London, along with Co-investigators from the Cancer Prevention Trials Unit at KCL, University of Edinburgh, University of Cardiff, University of Stirling, Queen Mary University, University of East Anglia and University of York.