We present an XMM-Newton observation of the radio galaxy 4C 23.56 at z = 2.48 which reveals extended X-ray emission coincident with the radio lobes spanning \sim 0.5 Mpc .
These are the largest X-ray-bright lobes known at z > 2 .
Under the assumption that these features result from inverse-Compton scattering of cosmic microwave background photons by relativistic electrons in the radio source lobes , the measured luminosity of L _ { \mathrm { 0.5 - 8 keV } } = 7.5 \times 10 ^ { 44 } erg s ^ { -1 } implies a minimum energy stored within the lobes of \sim 10 ^ { 59 } erg .
We discuss the potential of the large-scale radio/X-ray lobes to influence evolution of the host galaxy and proto-cluster environment at high redshift .