The integration into conceptual art of techniques inspired by Fluxus (the international aggregate of artists who saw indeterminacy as imaginatively and linguistically enabling) has, in turn, given rise to a specific line in British playwriting since the mid-1990s, as evidenced in plays by Martin Crimp, Sarah Kane, and Tim Crouch which gesture towards conceptual art, performance art, and the event score. In this article Emilie Morin brings to light the affinities between this artistic moment in contemporary British theatre and the international avant-garde. She discusses the shared interest of Crimp, Kane, and Crouch in indeterminacy and the fusion between artistic media, paying particular attention to Crouch's redefinition of the status of the modern artwork in his play for galleries England (2007). Critical recognition of the experimental mode in which these playwrights operate has remained subsumed under a non-specific appreciation of their relationship to conceptual art, leaving important questions of form and legacy unaddressed. Here, the proximity between this marginal trend in British playwriting and developments in experimental music and performance art exploring ideas of indeterminacy is highlighted, and the contemporary problematization of performance as event and concept is reconfigured in relation to the legacies of Marcel Duchamp, John Cage, and Fluxus. Emilie Morin is Lecturer in the Department of English and Related Literature at the University of York and the author of Samuel Beckett and the Problem of Irishness (Palgrave Macmillan, 2009). Her research interests lie in European modernism and the avant-garde.