Employee voice is an important source of organizational intelligence about possible problems in quality and patient safety, but effective systems for encouraging and supporting those who seek to speak up have remained elusive. In the English National Health Service, a novel role known as the 'Freedom to Speak Up Guardian' has been introduced to address this problem. We critically examine the role and its realization in practice, drawing on semi-structured interviews with 51 key individuals, including Guardians, clinicians, managers, policymakers, regulators and others. Operationalizing the new role in organizations was not straightforward, since it had to sit in a complex set of existing systems and processes. One response was to seek to bound the scope of Guardians, casting them in a signposting or coordinating role in relation to quality and safety concerns. However, the role proved hard to delimit, not least because the concerns most frequently voiced in practice differed in character from those anticipated in the role's development. Guardians were tasked with making sense of and dealing with issues that could not always straightforwardly be classified, deflected to the right system or escalated to the appropriate authority. Our analysis suggests that the role's potential contribution might be understood less as supporting whistleblowers who bear witness to clear-cut wrongdoing, and more as helping those with lower-level worries to construct their concerns and what to do with them. These findings have implications for how voice is understood, imagined and addressed in healthcare organizations.