Markwell was the first Rhodes Scholar and the second Australian to serve as Warden of Rhodes House (the global CEO of the Rhodes Trust and the Rhodes Scholarships). As Warden from 2009 to 2012, Markwell expanded activities for Rhodes Scholars in Oxford, expanded alumni communications, events and consultation, initiated governance reform and raised significant funds to support the Rhodes Scholarships. The appointments of several new Rhodes Trustees from around the world included John MacBain, who was later recognized as the "Second Century Founder" of the Rhodes Trust for a gift of £75 million. As well as discussing leadership, liberal education and collegiate education, Markwell's speeches drew attention to Cecil Rhodes' goal of promoting international peace. He initiated discussion on increasing the number of countries in which Rhodes Scholarships are offered, leading to the later creation of Rhodes Scholarships for China and other countries. He is credited with helping to initiate the review of undergraduate women's leadership at Princeton University, chaired by Nannerl O. Keohane, and of helping to make scholarships in South Africa open to women.
