  We present UV spectra of a small sample of high redshift active galaxies: the
hyperluminous, gravitationally lensed system SMM J02399-0136 (z=2.8) and three
powerful radio galaxies (z~2.5). Extended continuum and emission lines are
detected in all objects. The three radio galaxies present typical spectra with
dominant Lya and weaker CIV1550, HeII1640 and CIII]1909. The spectrum of SMM
J02399-0136 is strikingly different, showing relatively weak Lya and HeII and
strong NV1240 relative to the C lines.
  We find that the weakness of HeII can be explained if the intermediate
density narrow line region (n~10^{5-6} cm^-3 dominates the emission line
spectrum, rather than the more extended low density gas (n<100 cm^-3). The line
ratios of MRC2025-218 suggest that this is also the case in this object.
  MRC2025-218 and SMM J02399-0136 show the largest NV/HeII and NV/CIV values
found in high redshift radio galaxies. The failure of solar abundance models to
explain these line ratios and studies of metal abundances in high redshift
quasars and radio galaxies, suggest that nitrogen is overabundant in the
ionized gas of these objects. Alternative possibilities which we discuss
include NV emission from the broad line region and differential amplification
by a gravitational lens.
  We report the discovery of a PCygni profile in the CIV line in the spectrum
of MRC2025-218. We detect also CII1334.5 in absorption and PCygni profiles for
the lines SiIV1393.8,1402.8. We do not detect any purely photospheric stellar
lines. The nature of the absorption features is not clear. It could be due to
stars or an associated absorption line system.
