A method of transferring an established communication session in a telecommunications network, the communication session being established between one of a plurality of communication clients (710, 712, 910) associated with a user and a remote device associated with a remote party, the method comprising, at a call control system located in the signalling path for the established communication session: receiving, from a device associated with the user, a communication session transfer request, the communication session transfer request having been generated by and transmitted from the device; and initiating transfer of the established communication session from the one communication client in the plurality of communication clients to another communication client in the plurality of communication clients, wherein the another communication client is located on the device, and wherein the one communication client is located on a further device associated with the user, characterised by: at the call control system, in response to establishment of the communication session between the one communication client associated with a user and the remote device associated with the remote party, transmitting, to the device associated with the user, a notification that a communication session is currently being conducted between the one communication client associated with the user and the remote device associated with the remote party, wherein the notification is conducted on the basis of a preconfigured data set, specific to the user, identifying one or more of the plurality of communication clients associated with the user, and wherein the communication session transfer request is received at the call control system from the device associated with the user in response to user input received via a user interface of the device associated with the user, the user input indicating selection of at least one communication session transfer option, the at least one communication session transfer option having been displayed by the user interface in response to transmittal of the notification. receiving, from a device associated with the user, a communication session transfer request, the communication session transfer request having been generated by and transmitted from the device; and initiating transfer of the established communication session from the one communication client in the plurality of communication clients to another communication client in the plurality of communication clients, wherein the another communication client is located on the device, and wherein the one communication client is located on a further device associated with the user, characterised by: at the call control system, in response to establishment of the communication session between the one communication client associated with a user and the remote device associated with the remote party, transmitting, to the device associated with the user, a notification that a communication session is currently being conducted between the one communication client associated with the user and the remote device associated with the remote party, wherein the notification is conducted on the basis of a preconfigured data set, specific to the user, identifying one or more of the plurality of communication clients associated with the user, and wherein the communication session transfer request is received at the call control system from the device associated with the user in response to user input received via a user interface of the device associated with the user, the user input indicating selection of at least one communication session transfer option, the at least one communication session transfer option having been displayed by the user interface in response to transmittal of the notification. at the call control system, in response to establishment of the communication session between the one communication client associated with a user and the remote device associated with the remote party, transmitting, to the device associated with the user, a notification that a communication session is currently being conducted between the one communication client associated with the user and the remote device associated with the remote party, wherein the notification is conducted on the basis of a preconfigured data set, specific to the user, identifying one or more of the plurality of communication clients associated with the user, and wherein the communication session transfer request is received at the call control system from the device associated with the user in response to user input received via a user interface of the device associated with the user, the user input indicating selection of at least one communication session transfer option, the at least one communication session transfer option having been displayed by the user interface in response to transmittal of the notification.