1 INTRODUCTION  
2 CONSTRUCTION OF A MULTI WAVELENGTH CATALOGUE  
2.1 Source extraction and aperture selection  
2.2 Correction factors  
3 RESULTS  
3.1 SED modelling  
3.2 Assessing the fit quality  
3.3 Age and characteristic time  
3.4 Testing the dependence upon the assumed star formation model  
3.5 Mock photometry fits for two population SEDs  
4 DISCUSSION  
4.1 XLSSC 122 star formation history and its implications  
4.2 Link with the cluster assembly history  
5 SUMMARY