Yes / The importance of involving members of the public in the development, implementation and dissemination of research is increasingly recognised. There have been calls to share examples of how this can be done, and this paper responds by reporting how professional and lay researchers collaborated on a research study about falls prevention among older patients in English acute hospitals. It focuses on how they worked together in ways that valued all contributions, as envisaged in the UK standards for public involvement for better health and social care research. The paper is itself an example of working together, having been written by a team of lay and professional researchers. It draws on empirical evidence from evaluations they carried out about the extent to which the study took patient and public perspectives into account, as well as reflective statements they produced as co-authors, which, in turn, contributed to the end-of-project evaluation. Lay contributors' deep involvement in the research had a positive effect on the project and the individuals involved, but there were also difficulties. Positive impacts included lay contributors focusing the project on areas that matter most to patients and their families, improving the quality and relevance of outcomes by contributing to data analysis, and feeling they were 'honouring' their personal experience of the subject of study. Negative impacts included the potential for lay people to feel overwhelmed by the challenges involved in achieving the societal or organisational changes necessary to address research issues, which can cause them to question their rationale for public involvement. The paper concludes with practical recommendations for working together effectively in research. These cover the need to discuss the potential emotional impacts of such work with lay candidates during recruitment and induction and to support lay people with these impacts throughout projects; finding ways to address power imbalances and practical challenges; and tips on facilitating processes within lay groups, especially relational processes like the development of mutual trust. / Funded by the National Institute for Health Research (NIHR) Health and Social Care Delivery Research (HSDR) Programme (Project Number NIHR129488).