Surveillance, especially using biometric systems, threatens the privacy of individuals. Accountability is an established approach to supporting privacy in general, but it must follow a rigorous process and involve close scrutiny of actual data handling practice to be effective. In this paper, we consider a specific, real-world biometric surveillance system, based on camcorders and bodyprint identification. We show how formalisation can be used to achieve the required level of rigour and exemplify how our formal approach to accountability-in the sense of verifiable compliance with personal data handling policies-supports the privacy of individuals monitored by the system. The formal accountability framework is general enough to be reusable in other settings.