Then there were seven: a commentary on creating a public involvement strategy group for a policy research unit in behavioural science.

The Policy Research Unit in Behavioural Science (PRU-BS) was formed in early 2019, funded by the National Institute for Health and Care Research (NIHR). The aim of the unit is to advise the government on the use of behavioural science (the study of human behaviour) to inform health and social care policy. From the outset the aim was to embed PPI in all aspects of the unit's work from the governance and direction of the unit to the individual research projects it conducts. As behavioural science cuts across all aspects of health, recruiting members of the public to work within the PRU-BS required careful thought. In this paper we describe the processes of recruiting to our PPI Strategy Group, the induction and training, and the ways in which we worked to develop the group and become embedded within the unit. Lastly, we present several recommendations based on our experiences of forming the PPI Strategy Group. Although this is aimed primarily at those contemplating setting up a group whose remit extends beyond a single research project, we hope this will be a useful resource for the public, researchers and others working in PPI.