9C J1503+4528 is a very young CSS radio galaxy , with an age of order 10 ^ { 4 } years .
This source is therefore an ideal laboratory for the study of the intrinsic host galaxy/IGM properties , interactions between the radio source and surrounding ISM , links between star formation and AGN activity and the radio source triggering mechanism .
Here we present the results of a spectroscopic analysis of this source , considering each of these aspects of radio source physics .

We find that shock ionization by the young radio source is important in the central regions of the galaxy on scales similar to that of the radio source itself , whilst evidence for an AGN ionization cone is observed at greater distances .
Line and continuum features require the presence of a young stellar population , the best-fit model for which implies an age of 5 \times 10 ^ { 6 } years , significantly older than the radio source .

Most interestingly , the relative sizes of radio source and extended emission line region suggest that both AGN and radio source are triggered at approximately the same time .

If both the triggering of the radio source activity and the formation of the young stellar population had the same underlying cause , this source provides a sequence for the events surrounding the triggering process .
We propose that the AGN activity in 9C J1503+4528 was caused by a relatively minor interaction , and that a super-massive black hole powering the radio jets must have been in place before the AGN was triggered .