A portable electronic device comprising a service provision unit capable of providing a service to a user, a communication unit capable of receiving authorization data from an authorization device and a validation unit capable of analyzing the received authorization data to determine whether it meets a validation requirement and being arranged to inhibit provision of the service by the service provision unit if the authorization data does not meet the validation requirement, the communication unit being arranged to receive authorization data from the authorization device and the validation unit being arranged to analyze the received authorization data whenever the communication unit and the authorization device are capable of communicating with each other.