The X-ray-Infrared/Submillimetre Connection and the Legacy Era of   Cosmology
  We review some recent results on the identification and characterisation of Active Galactic Nuclei (AGN) obtained by cross correlating X-ray surveys with infrared and submillimetre surveys. We also look toward the scientific gains that could be achieved from an XMM-Newton survey of the medium-deep legacy fields that are being observed at ~1-850um. 
D.M. Alexander