A method of determining the temperature of an inner section of a cylinder head (204) in an internal combustion engine. The engine comprises: at least one piston cylinder (201) which cylinder is formed at least in part by the cylinder head (204); and at least one jacket (205), the jacket having a proximal wall and a distal wall. The proximal wall of the jacket is proximate to the piston cylinder (201) and the distal wall of the jacket is distal to the piston cylinder (201). The method comprises: providing a temperature sensor (202) on the distal wall of the jacket; receiving a first temperature measurement from the temperature sensor (202); and inferring the temperature of the inner section of the cylinder head (204) from the first temperature measurement.