A gateway delivery function module for use in a system for intercepting wireless communications, the gateway delivery function module being configured: to provision one or more surveillance flags to a home location register coupled to a plurality of mobile switching centers so that the surveillance flags in the home location register indicate one or more aspects to be monitored of the wireless communications of a subscriber under surveillance served by the home location register, the mobile switching centres reading the flags stored in the home location register or referring to a locally stored copy of the flags for a call involving the subscriber under surveillance; to receive call associated information for the subscriber under surveillance in accordance with one or more of the surveillance flags; to access a database containing provisioning data indicating which calls of the subscriber are authorised to be monitored; to determine, in accordance with the provisioning data and the call associated information, whether delivery of call associated information or call content for a particular wireless communication is authorized to be delivered to a particular call intercept destination; to control, in accordance with the determination made with respect to the particular wireless communication and the particular call intercept destination, a delivery function module, coupled to the plurality of mobile switching centers, to receive call content of the particular wireless communication therefrom and coupled to the gateway delivery function module to receive call associated information of the particular wireless communication therefrom, to forward the call associated information of the particular wireless communication and call content of the particular wireless communication to the particular call intercept destination. to provision one or more surveillance flags to a home location register coupled to a plurality of mobile switching centers so that the surveillance flags in the home location register indicate one or more aspects to be monitored of the wireless communications of a subscriber under surveillance served by the home location register, the mobile switching centres reading the flags stored in the home location register or referring to a locally stored copy of the flags for a call involving the subscriber under surveillance; to receive call associated information for the subscriber under surveillance in accordance with one or more of the surveillance flags; to access a database containing provisioning data indicating which calls of the subscriber are authorised to be monitored; to determine, in accordance with the provisioning data and the call associated information, whether delivery of call associated information or call content for a particular wireless communication is authorized to be delivered to a particular call intercept destination; to control, in accordance with the determination made with respect to the particular wireless communication and the particular call intercept destination, a delivery function module, coupled to the plurality of mobile switching centers, to receive call content of the particular wireless communication therefrom and coupled to the gateway delivery function module to receive call associated information of the particular wireless communication therefrom, to forward the call associated information of the particular wireless communication and call content of the particular wireless communication to the particular call intercept destination.