  Discerning the exact nature of the faint (sub-mJy) radio population has been
historically difficult due to the low luminosity of these sources at most
wavelengths. Using deep observations from Chandra/XMM-Newton/Spitzer and ground
based follow up we are able to disentangle the AGN and star-forming populations
for the first time in a deep multi-frequency GMRT/VLA/MERLIN Survey. The many
diagnostics include radio luminosity, morphology, radio to mid-IR flux density
ratios, radio to optical flux density ratios and radio spectral indices.
Further diagnostics, e.g. optical spectra X-ray spectra/hardness ratios, IR
colours indicate the presence of the AGN {\em independent} of whether the radio
emission is powered by AGN or star-formation. We are able to examine the
star-formation history of the universe up to z=2.5 in a unique way based on an
unbiased star-formation rate indicator, radio luminosity. This work provides an
alternative perspective on the distribution of star-formation by mass,
``downsizing'' and allows us to examine the prevalence of AGN in star-bursts.
