A method of operating a terminal device and a base station in a wireless telecommunications system to communicate with one another using a primary component carrier operating on radio resources within a first frequency band and a secondary component carrier operating on radio resources within a second frequency band. The terminal device makes measurements of radio usage in the second frequency band, and transmits an indication of the measurements to the base station. The base station then establishes a configuration setting for the secondary component carrier. The configuration setting is associated with a validity period during which the base station communicates data to the terminal device using the primary component carrier and the secondary component carrier operating in accordance with its configuration setting.