This introduces the Marlborough-Godolphin partnership as not just a political alliance, but a close friendship founded on ideals of platonic love and heroic virtue. It reviews the various discourses of friendship, noting the cultural influences (the essayists Montaigne, Sir William Temple, Saint-Évremond, as well as heroic drama and opera) which carried the ideal forward, but with the growing sense that it must prove itself in actual human transactions. It suggests that studying the Marlborough-Godolphin friendship as it proved itself in war abroad and party conflict at home is revealing of two historical figures whom historians have often found enigmatic, though in the end their commitment to it contributed to their short-term failure as well as their longer-term success. The distinction between friendship and royal favour is also touched on.