The value of patient and public involvement (PPI) during the earliest stages of clinical trial development, and prior to the award of substantive funding, is widely recognised. However, it is often under-resourced and PPI processes during this phase are rarely reported in detail. Having benefitted from seed funding to develop an international clinical trial proposal, we sought to describe and appraise PPI activities and processes that support pre-award co-development. A 12-month "accelerator" award facilitated development of a substantive funding application to deliver the Rheumatoid Arthritis Prevention PlatfORm Trial (RAPPORT), conceived to prioritise preventative interventions for people at risk of RA. PPI partners, including individuals at risk of rheumatoid arthritis (RA), RA patients, relatives and members of the public, provided feedback on key trial design issues through online meetings, a feedback form and emails. PPI processes employed during the one-year accelerator project were thereafter evaluated by PPI partners using an anonymous online feedback form with reference to National Institute of Health and Care Research (NIHR) UK standards for public involvement in research. Sixteen out of the 25-strong PPI partner panel completed an online feedback form (64%). Respondents perceived PPI processes positively in relation to all NIHR standard domains. Several key facilitators and challenges were identified, including the need for adequate PPI funding during pre-award phases of research, strategies for creating an inclusive environment, flexibility around levels of involvement, and challenges in achieving representatively diverse participation, and the importance of communicating transparent processes for role-assignment and time-reimbursement. In general, RAPPORT was considered an example of PPI well done, and in line with UK standards for public involvement in research. Facilitators and challenges of relevance for the development of future translational and clinical trial funding applications are highlighted.