AbstractBackgroundSome interventions are developed from practice, and implemented before evidence of effect is determined, or the intervention is fully specified. An example is Namaste Care, a multi-component intervention for people with advanced dementia, delivered in care home, community, hospital and hospice settings. This paper describes the development of an intervention description, guide and training package to support implementation of Namaste Care within the context of a feasibility trial. This allows fidelity to be determined within the trial, and for intervention users to understand how similar their implementation is to that which was studied.MethodsA four-stage approach: a) Collating existing intervention materials and drawing from programme theory developed from a realist review to draft an intervention description. b) Exploring readability, comprehensibility and utility with staff who had not experienced Namaste Care. c) Using modified nominal group techniques with those with Namaste Care experience to refine and prioritise the intervention implementation materials. d) Final refinement with a patient and public involvement panel.ResultsEighteen nursing care home staff, one carer, one volunteer and five members of our public involvement panel were involved across the study steps. A 16-page A4 booklet was designed, with flow charts, graphics and colour coded information to ease navigation through the document. This was supplemented by infographics, and a training package. The guide describes the boundaries of the intervention and how to implement it, whilst retaining the flexible spirit of the Namaste Care intervention.ConclusionsThere is little attention paid to how best to specify complex interventions that have already been organically implemented in practice. This four-stage process may have utility for context specific adaptation or description of existing, but untested, interventions. A robust, agreed, intervention and implementation description should enable a high-quality future trial. If an effect is determined, flexible practice implementation should be enabled through having a clear, evidence-based guide.