A communication event is established between an initiating device and a responding device under the control of a remote communications controller. In a pre-communication event establishment phase, a secure connection is established between the initiating device and the communications controller, and session key negotiation messages are exchanged between the initiating device and the communications controller via the secure connection to obtain session key data in an electronic storage location accessible to the initiating device. The secure connection terminates once the session key data has been obtained. In a subsequent communication event establishment phase—after the session key data has been obtained and the secure connection has terminated in the pre-establishment phase—a communication event request is transmitted from the initiating device to the communications controller comprising a payload encrypted with the session key data.