There is a body of literature suggesting that mindfulness or meditation interventions for leaders and managers has/would have a positive impact on leaders' own wellbeing, their leadership capability, and their direct reports. However, no systematic review had previously been conducted examining the benefits of such interventions. The purpose of the first study in this thesis was therefore to systematically review research on mindfulness or meditation interventions for managers and leaders. The review identified 19 studies that met the inclusion criteria. Findings indicate some encouraging signs that mindfulness and meditation interventions may improve aspects of leaders'/managers' wellbeing and resilience, and leadership capability, but research results are very variable in quality and strength, and there was no evidence on benefits for participants' direct reports. The studies reviewed explored a diversity of interventions, but provided little insight into which mindfulness and meditation interventions for managers and leaders are most effective, in what context they are best applied, or for whom they are most suitable. While the sub-set of studies that measured mindfulness found that the interventions used did increase participants' mindfulness, there was no exploration of whether improved mindfulness was the mechanism by which other positive outcomes were achieved. Given the interpersonal nature of leadership, an interpersonal form of mindfulness has the potential to offer leaders and managers benefits over and above those provided by intrapersonal mindfulness. The second study in this thesis therefore set out to explore the possibility of adapting a particular intervention, Interpersonal Mindfulness (IM), which is based on Insight Dialogue (Kramer 2007), for application in leadership development. As scientist-practitioners, we chose a Delphi research methodology, in order to apply a systematic academic research process to consulting and achieving consensus between expert practitioners in the field, in order to explore the potential application of IM in leadership development. Our aims were: firstly, to create a shared understanding of the necessary components of an IM programme for leadership development; and, secondly, to create guidance for those who might offer such a programme in practice. Through four phases of data gathering and feedback, we achieved consensus between 39 experts on guidance text covering: development of an IM-based leadership development programme, contextual factors that will act as facilitators or barriers, and selection and screening of participants. The intention is that this guidance will impact practice though supporting implementation of coherent, consistent IM-based leadership development, sensitive both to its origins and to the context; and that our methodology and learning support others in impacting the world outside academic research.