An apparatus for monitoring the condition of a pneumatic tyre, the apparatus comprising: at least one pressure sensor to measure an internal pressure within the tyre; at least one speed sensor to measure a rotational speed of the tyre; and a controller that is configured to receive data from the pressure sensor and the speed sensor and output indications related to a condition of the tyre; the controller determining the output indications by: tracking the internal pressure with respect to time during use of the tyre; identifying at least one change in internal tyre pressure in a time interval between a first reference time and a second reference time, the reference times corresponding to points at which the speed sensor indicates different rotational speeds of the tyre, characterized in that: one of the first reference time or the second reference time is selected to correspond to a time when the speed sensor indicates that the tyre is stationary, and the other of the first reference time and second reference time is selected to correspond to a local maximum rotational speed; and monitoring the pressure change as a function of rotational speed of the tyre to provide an indicator of tyre condition. at least one pressure sensor to measure an internal pressure within the tyre; at least one speed sensor to measure a rotational speed of the tyre; and a controller that is configured to receive data from the pressure sensor and the speed sensor and output indications related to a condition of the tyre; the controller determining the output indications by: tracking the internal pressure with respect to time during use of the tyre; identifying at least one change in internal tyre pressure in a time interval between a first reference time and a second reference time, the reference times corresponding to points at which the speed sensor indicates different rotational speeds of the tyre, characterized in that: one of the first reference time or the second reference time is selected to correspond to a time when the speed sensor indicates that the tyre is stationary, and the other of the first reference time and second reference time is selected to correspond to a local maximum rotational speed; and monitoring the pressure change as a function of rotational speed of the tyre to provide an indicator of tyre condition. tracking the internal pressure with respect to time during use of the tyre; identifying at least one change in internal tyre pressure in a time interval between a first reference time and a second reference time, the reference times corresponding to points at which the speed sensor indicates different rotational speeds of the tyre, characterized in that: one of the first reference time or the second reference time is selected to correspond to a time when the speed sensor indicates that the tyre is stationary, and the other of the first reference time and second reference time is selected to correspond to a local maximum rotational speed; and monitoring the pressure change as a function of rotational speed of the tyre to provide an indicator of tyre condition. one of the first reference time or the second reference time is selected to correspond to a time when the speed sensor indicates that the tyre is stationary, and the other of the first reference time and second reference time is selected to correspond to a local maximum rotational speed; and monitoring the pressure change as a function of rotational speed of the tyre to provide an indicator of tyre condition.