intrinsically luminous optical-UV AGN in the radio population we associate with FRI sources (e.g. Vardoulaki et al. 2008). We therefore model their infrared SEDs with a template representing host galaxy starlight only, which we produced using the GALSYNTH online interface to the GRASIL code developed by Silva et al. (1998). The models are based on their ‘Elliptical model’, which gives the evolving SED (taking account of dust reprocessing) of a stellar population formed in a burst of 1 Gyr duration (see description of this particular model at http://adlibitum.oat.ts.astro.it/silva/grasil/modlib/modlib.html). We generated models with ages separated by 0.1 Gyr for 0.1–1.5 Gyr, and by 1 Gyr for ages 2–13 Gyr. We assume formation redshifts distributed uniformly in the range z=10–20, and select the template nearest in age at the redshift of the galaxy under consideration. To normalise the SEDs, we draw upon the bivariate 1400 MHz–K-band luminosity function derived by Mauch & Sadler (2007) for a local sample: given a radio power, the absolute K-band magnitude is drawn from a Gaussian distribution of specified mean and variance and this is used to normalise the SED. For simplicity, we assume the same (local) relation between K-band luminosity and radio power at all redshifts. 