  Deep radio observations at 5 and 8 GHz are presented of a complete sample of
11 radio galaxies with redshifts 0.85 < z < 1.5, selected from the 6C sample of
Eales. The radio data, taken using the VLA in A, B and C array configurations,
provide a best angular resolution of 0.25'' and reach an rms noise level of
order 20 microJy. Radio core candidates are detected in 8 of the 11 sources. 9
of the 11 sources display deviations from `standard double radio source'
morphologies, with multiple hotspots or a hotspot withdrawn from the leading
edge of the radio emission. The sources are typically polarised at the 5 to 15%
level. The mean rotation measures of the individual lobes are less than 50
rad/m^2 but strong asymmetries between the two lobes indicate that the Faraday
rotation does not have a Milky Way origin; rather, the distant 6C radio sources
lie in a relatively dense clumpy environment. The sources are compared with the
more radio powerful distant 3CR radio galaxies and with low redshift sources.
The ratio of core to extended radio flux is almost independent of the radio
source size and only weakly inversely correlated with the total radio power.
This indicates that the high radio luminosity of the most powerful radio
sources must originate in the AGN, in contrast to the suggestion that they are
so luminous only due to confinement by a dense surrounding environment.
Environmental effects play a secondary role. (Abridged)
