This paper is concerned with the distant radio galaxies in a sample of bright sources selected at 178 MHz by Laing, Riley & Longair (1982). This sample is 96% complete for sources with θ < 10′ and the bias of the 3CR catalogue against sources of large angular size has also been reduced. Deep optical searches have located many candidate identifications, but the probability of a chance coincidence with an unrelated object is appreciable, especially in the faintest cases, unless the area to be searched is small. We have therefore mapped the sources with candidate identifications having V > 20, using the VLA at a wavelength of 6 cm (Laing, Owen & Puschell, in preparation), in order to search for radio cores. We have so far located cores in 16/23 sources and set 5σ upper limits of 0.6 mJy for the remainder. None of the cores had been detected previously. In all cases, the cores coincide with optical objects, although one source (3C 340) had been misidentified. Several ambiguities have now been resolved.