1. A method of performing one of authorising individuals and identifying individuals using a biometric security system comprising the steps of: storing a system security level; determining an initial security level for a plurality of individuals, the initial security level determined such that the actual security level of the system is at least the stored system security level; storing a current security level in association with at least one of an identification of an individual and an authorisation of an individual; performing at least one of authorising individuals and identifying individuals using the biometric security system to determine a likelihood that the individual is accurately authorised or identified; determining individuals who are consistently authorised or identified, the likelihood indicative of a higher level of security than the current security level associated with said individuals; increasing the current security level associated with the determined individuals; determining individuals who are consistently authorised or identified identified, the likelihood indicative of a lower level of security than the current security level associated with said individuals; and, lowering the current security level associated with the determined individuals such that the resulting actual system security level is at least the stored system security level.