Robert Testwood (c. 1490–1543), professional singer and evangelical mischief-maker, is the subject of many colourful anecdotes in Foxe’s Acts and monuments, including a scene in which Testwood mocks the veneration of the Virgin Mary by sabotaging a performance of a polyphonic motet in St George’s Chapel, Windsor. This act of sonic iconoclasm can be dated securely to mid-May 1538. It can be placed in a rich context of surveillance, propaganda, dissent and counter-dissent among the liturgical staff of St George’s as they navigated the changes of the early Reformation.