Are modern constitutional structures evolving, internationally, to recognise a discernable fourth species of governmental power, alongside the traditions of legislative, executive and judical power: a specific 'integrity' function of government, reflected in an increasingly prevalent fourth 'integrity branch'? This panel, incorporating the 2018 Presidential Address of the Australian Political Studies Association, will examine both theoretical roots and contemporary trends and challenges for the ways in which government continues to evolve in response to democratic demands for integrity and accountability, especially in the face of growing concentrations in executive power, elite self-interest, state capture and corruption awareness across political systems. What do traditional Montesqieuean principles of the separation of powers have to say about these trends? How does the value increasingly placed by citizens on integrity agency independence, compare with that traditionally placed on judicial independence, and how can these values best be reconciled in the ongoing search for more accountable and corruption-resistant forms of government? What new principles should guide the design, development and acceptance of these evolutions in governance?