An interesting article by Steve Iliffe and Jill Manthorpe in the British Journal of General Practice 2019; 69 (679): 52-53. https://doi.org/10.3399/bjgp19X700817 says the following:

Leadership has become fashionable in health services around the world. The National Health Service (NHS) has led the way with a Medical Leadership Competency Framework jointly developed by the NHS Institute of Innovation and Improvement and the Academy of Medical Royal Colleges in 2010, with the intention of embedding it in undergraduate and postgraduate curricula. According to Warren and Carnall: ‘It is indisputable that to deliver high-quality care consistently to patients requires, among many other factors, good medical leadership’.

Yet the empirical evidence for the importance of ‘leadership’ as a distinct characteristic is thin, and the return on investment in leadership training programmes remains largely unmeasured worldwide.  A systematic review of the evidence about leadership says politely: ‘the concept of leadership … seems not to be fully developed’. A more recent international review of leadership styles, models, and theories, found health services leadership could be evaluated as ‘transformational’, ‘situational’, ‘servant–leader relationship’, or ‘authentic’.  Less common styles were ‘quantum’ (reflective), ‘charismatic’, and ‘clinical’. The plethora of leadership styles suggests that medical leadership has multiple meanings, including the ‘informal leadership’ observed in some Clinical Commissioning Groups.