MHz)[W/Hz/sr]} - 26.55)$ mag (following Willott et al. 2003, Fig. 3).

In principle, the evolving elliptical template from the GRASIL library should self-consistently reproduce the far-infrared dust emission. To compare with this, we included in addition a far-infrared dust component to explicitly match the starburst properties to the sub-millimetre observations of radio galaxies and quasars by Archibald et al. (2001), Willott et al. (2002) and Reuland et al. (2004). From Willott et al. (2002), the radio quasars appear to be a factor of several brighter than the radio galaxies at 850. In Grimes, Willott & Rawlings (2005), this was enshrined as a universal relationship between L(\[OIII\]$\lambda5007$) \[W\] and L(850) \[W/Hz/sr\]:

$$\rm{log L(850\micron)} = -2.5753 + 0.682\rm{log L([OIII]\lambda5007}),$$

with additional scatter drawn from a gaussian of $\sigma = 0.44$. With this normalisation, we adopt a modified blackbody with $\beta = 1.95$, $T=41$, as found by Priddey & McMahon (2001) for high-redshift quasars. Archibald et al. (2001) found L(850 (rest)) to be a strongly increasing function of redshift, but for our adopted SED parameters, the redshift dependence is a more modest $(1+z)^{1.5}$ (see Reuland et al., Fig. 4); this dependence is added to eqn. (8) and normalised at $z=2.5$. There is evidence 