  We present the results of XMM-Newton observations of three high-redshift
powerful radio galaxies 3C 184, 3C 292 and 3C 322. Although none of the sources
lies in as rich an X-ray-emitting environment as is seen for some powerful
radio galaxies at low redshift, the environments provide sufficient pressure to
confine the radio lobes. The weak gas emission is particularly interesting for
3C 184, where a gravitational arc is seen, suggesting the presence of a massive
cluster. Here Chandra data complement the XMM-Newton measurements by spatially
separating X-rays from the extended atmosphere, the nucleus and the small-scale
radio source. For 3C 292 the X-ray-emitting gas has a temperature of ~2 keV and
luminosity of 6.5E43 erg/s, characteristic of a poor cluster. In all three
cases, structures where the magnetic-field strength can be estimated through
combining measurements of radio-synchrotron and inverse-Compton-X-ray emission,
are consistent with being in a state of minimum total energy. 3C 184 and 3C 292
(and possibly 3C 322) have a heavily absorbed component of nuclear emission of
N_H ~ $ few 10^{23} cm^{-2}.
