Context : Aims : Gas cooling in the centre of massive galaxy clusters is believed to feed the most powerful active galactic nuclei in the Universe . How often clusters at high redshift show such cool cores has still to be explored by current and upcoming X-ray telescopes . Methods : We correlated extended X-ray emissions from the second XMM- Newton  source catalogue with SDSS data to particularly identify distant clusters . 2XMM J100451.6+411627 is a candidate luminous enough to obtain its redshift and temperature from the X-ray spectrum . We also determine the surface luminosity profile and estimate the temperature in a few spherical bins . The analysis is complemented by a Subaru g ^ { \prime } r ^ { \prime } i ^ { \prime } -image . Results : 2XMM J100451.6+411627 has a redshift a redshift of z = 0.82 \pm 0.02 and a temperature of k _ { B } T = 4.2 \pm 0.4 \ > { keV } . A double- \beta profile fit yields a highly concentrated surface brightness , c _ { SB } = 0.32 , i. e ,   the clusters hosts very likely a strong cool core . This is supported by the relaxed morphology of the cluster and an central temperature decrease . Conclusions :