An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 is presented .
We find that the spectrum is well fitted by a power law of canonical slope ( \Gamma \sim 1.9 ) and 3 blackbody components ( to model the strong soft excess ) .
The XMM data are compared and contrasted with observations by ROSAT in 1992 and by ASCA and BeppoSAX in 1996 .
We find that the overall X-ray spectrum has changed substantially over the period , and suggest that the changes are driven by the soft X-ray component .
When bright , as in our XMM-Newton observation , it appears that the enhanced soft flux cools the Comptonising corona , causing the 2–10 keV power law to assume a ‘ typical ’ slope , in contrast to the unusually hard ( ‘ photon-starved ’ ) spectra observed by ASCA and BeppoSAX four years earlier .