A terminal device configured to receive a radio signal from which measurements can be used to assist in determining a position of the terminal device. The terminal device detects one or more system information blocks carrying position assistance information transmitted from the infrastructure equipment and estimates the position of the terminal device by combining the identified position assistance information with the radio signal received by the position detection receiver circuitry. Furthermore the terminal device receives from the infrastructure equipment an indication of relative risk that the position assistance information will change, and in response to the indication of the relative risk that the position assistance information will change to adapt the receiving of the one or more system information blocks to receive an updated version of the position assistance information in accordance with the relative risk.