This is the concluding article of a series of four articles, which started by introducing the concept of the "fully-functioning university" in 2008. Subsequent articles have looked at the consequences of this concept for the higher education of students and the advancement of knowledge. This article is about the fully-functioning university and its contribution to the service part of the tripartite mission; the "third leg". Its main aim is to identify how social engagement can best contribute to the tripartite mission in total. The main conclusions are that: (1) there is a set of questions that can be used to help enlarge the contribution of third leg work to the advancement of knowledge, (2) there is another set of questions that can be used to help enlarge the contribution of third leg projects to the higher education of students and (3) greater use of project-based thinking within the domain of the third leg activities can support research-led, and hence evidence-based, practices and outcomes. The article ends with some implications of these conclusions and some questions surfaced by this enquiry.