Schemes for supporting device-to-device, D2D, communications between terminal devices in a wireless telecommunication system. A network entity, e.g. a base station, establishes a set pool of radio resources to be reserved for use for D2D communications and communicates an indication of these resources to terminal devices. On an ongoing basis the network entity monitors the extent to which the set of radio resources reserved for D2D communications is being used, for example based on feedback received from terminal devices or its own measurements. If it is determined the set of radio resources reserved for D2D communications is being under-utilized or over-utilized, the network entity may establish an updated set of radio resources to be used for D2D communications, and communicate this to the terminal devices. Thus a mechanism is provided for dynamically adjusting the size of a set of resources available for D2D communications in response to changing resource utilization.