1. A computer-implemented method of determining policy control decisions in a cellular mobile telecommunications network, the method comprising the steps of: a policy management system receiving a predictive indicator from a forecasting system, wherein the predictive indicator includes predictive network resource utilization information indicating times and durations for which resource utilization in the cellular mobile telecommunications network is expected to deviate from a basic resource utilization range for a defined part of the cellular mobile telecommunications network; responsive to receiving a service request from a gateway, said policy management system determining a policy decision based on the predictive indicator, the policy decision determining whether to allow or deny the service request; and said policy management system sending the policy decision to the gateway; wherein the policy management system is further arranged to notify the forecasting system of an identifier of resources whose resource utilization is likely to be affected by the policy decision based on the predictive indicator, and sent to the gateway.