The National Institute for Health and Care Excellence (NICE) recommend that men with prostate cancer on androgen deprivation therapy (ADT) are offered twice weekly supervised aerobic and resistance exercise to address side effects of treatment. However, supervised exercise is not routinely offered in standard clinical practice. The STAMINA programme grant for applied research (PGfAR) has been designed to evaluate whether this recommendation can be delivered within standard NHS care. This paper describes how future implementation of NICE recommendations within the NHS was explored during complex intervention development to enable evaluation of a lifestyle intervention. Two stakeholder workshops were conducted to explore factors pertinent to future implementation of the STAMINA Lifestyle intervention (SLI). Normalisation Process Theory (NPT) provided the theoretical framework for discussion and analysis. Stakeholder workshop 1 focussed on intervention coherence and buy-in. Stakeholder workshop 2 explored barriers and facilitators for embedding SLI into the context of the NHS, with delivery partner Nuffield Health, in the future. Workshops were attended by healthcare professionals (n = 16), exercise professionals (n = 17), members of public involved in PPI including patients (n = 12), health psychologists (n = 2), clinical commissioners (n = 4), cancer charities (n = 3), a cancer alliance (n = 1) and health economist (n = 1). Stakeholders agreed that professional training packages should emphasise the uniqueness of the SLI and underpinning theory and evidence (Coherence). To further engagement, the use of STAMINA champions and information about the delivery partner were recommended to enhance confidence and knowledge (Cognitive participation). Furthermore, a simple communication (Collective Action) and progress reporting system (Reflexive Monitoring) was suggested to fit into existing infrastructure within the NHS and community partner. Application of NPT within two stakeholder workshops enhanced complex intervention development. Context-specific strategies to support implementation of SLI within the context of a trial were proposed, sensed-checked, and considered acceptable. The organisational implications of embedding and sustaining the intervention in preparation for wider NHS roll-out were considered (if proven to be effective) and will be explored in the qualitative component of a process evaluation underpinned by NPT. (ISRCTN: 46385239 ). Registered on July 30, 2020.