Leadership of complex virtual teams is a growing challenge that can test the capabilities of project managers to the limit. How best to meet this challenge in the years to come? This paper introduces a rigorously developed and tested Process Reference Model (PRM) and associated Assessment Model for the leadership of complex virtual teams. Originally developed for the Software Engineering domain, it has now been generalised for use in other domains, and for many kinds of team. Using proven process modelling techniques developed used in the Model-Based Process Improvement field, the Leadership PRM describes the attributes that a project manager should possess, and the activities they should perform if they are to successfully lead teams. This paper asserts that leadership is a skill that can be learned and developed over time to a higher level of competence. It distinguishes management from leadership by suggesting that managers coordinate the activities of team members in the pursuit of goals, while leaders extend this management capability by knowing how to motivate team members to want to do what it is the leader wants them to do. It outlines how a manager can become a leader while becoming a better manager.