A user device comprising: a display; a network interface configured to transmit and receive video data between the user device and a communication network during a multiparty video call between a user of said user device and a plurality of further users; a memory storing information identifying a plurality of avatar images each representing one of said plurality of further users; and one or more processors configured to run a communication client application operable to perform a processing required at the user device in order for the user device to communicate over said communication network and also operable during said multiparty video call to: display video data received from said plurality of further users, as part of the video call, in a first user interface window on said display; detect during the multiparty video call an input selection by the user of said user device to navigate away from the first user interface window to a second user interface window of said communication client application, wherein said second user interface window comprises a display location for the display of one avatar image representing one of said plurality of further users and wherein said one avatar image is displayed at that location when the second user interface window is accessed by the user when not conducting a video call; and query said memory to determine a display location for the display of video data received from said plurality of further users, and in response to said query, display the second user interface window on the display and control the video data received from the one of said plurality of further users represented by said one avatar image of the second user interface window to be displayed at the display location of said one avatar image, in place of the avatar image that would otherwise be displayed in the second user interface window if the second user interface window was accessed by the user when not conducting a video call. a display; a network interface configured to transmit and receive video data between the user device and a communication network during a multiparty video call between a user of said user device and a plurality of further users; a memory storing information identifying a plurality of avatar images each representing one of said plurality of further users; and one or more processors configured to run a communication client application operable to perform a processing required at the user device in order for the user device to communicate over said communication network and also operable during said multiparty video call to: display video data received from said plurality of further users, as part of the video call, in a first user interface window on said display; detect during the multiparty video call an input selection by the user of said user device to navigate away from the first user interface window to a second user interface window of said communication client application, wherein said second user interface window comprises a display location for the display of one avatar image representing one of said plurality of further users and wherein said one avatar image is displayed at that location when the second user interface window is accessed by the user when not conducting a video call; and query said memory to determine a display location for the display of video data received from said plurality of further users, and in response to said query, display the second user interface window on the display and control the video data received from the one of said plurality of further users represented by said one avatar image of the second user interface window to be displayed at the display location of said one avatar image, in place of the avatar image that would otherwise be displayed in the second user interface window if the second user interface window was accessed by the user when not conducting a video call. display video data received from said plurality of further users, as part of the video call, in a first user interface window on said display; detect during the multiparty video call an input selection by the user of said user device to navigate away from the first user interface window to a second user interface window of said communication client application, wherein said second user interface window comprises a display location for the display of one avatar image representing one of said plurality of further users and wherein said one avatar image is displayed at that location when the second user interface window is accessed by the user when not conducting a video call; and query said memory to determine a display location for the display of video data received from said plurality of further users, and in response to said query, display the second user interface window on the display and control the video data received from the one of said plurality of further users represented by said one avatar image of the second user interface window to be displayed at the display location of said one avatar image, in place of the avatar image that would otherwise be displayed in the second user interface window if the second user interface window was accessed by the user when not conducting a video call.