Size of the mid-infrared emitter as a function of the X-ray luminosity, taken as a proxy for the intrinsic AGN luminosity. Colours and symbols are as in Fig. 3. The red dashed line shows the inner radius of the torus derived from reverberation measurements and near-infrared interferometry. The individual measurements of near-infrared radii are plotted as red points and were taken from Suganuma et al. (2006). For these, only the sources common to our sample are labelled.