  Active galaxies are the most powerful engines in the Universe for converting
gravitational energy into radiation, and their study at all epochs of evolution
is therefore important. Powerful radio-loud quasars and radio galaxies have the
added advantage that, since their radio jets need X-ray-emitting gas as a
medium in which to propagate, the sources can be used as cosmological probes to
trace significant atmospheres at high redshift. The radio emission can be used
as a measure of source orientation, and sensitive X-ray measurements,
especially when used in combination with multi-wavelength data, can be used to
derive important results on the physical structures on a range of sizes from
the cores to the large-scale components. In this paper we present new results
on a significant sample of powerful radio galaxies and quasars at z > 0.5,
drawn from the 3CRR catalogue and selected to sample a full range of source
orientation. Using high-quality observations from XMM-Newton and Chandra, we
discuss the X-ray properties of the cores, jets, lobes and cluster gas, and,
through the incorporation of multi-wavelength data, draw conclusions about the
nature of the emission from the different components.
