  We present VLT-UVES echelle spectra of the Lyman alpha emission and
absorption in five radio galaxies at redshifts z=2.55-4.1. Together with data
from our pilot study, we have a sample of 7 such systems with radio source
sizes ~ 1-90 kpc with which to address the origin of the absorbing gas. Echelle
resolution again reveals that some systems with N_HI>1E18 cm^-2 in lower
resolution data in fact consist of several weaker absorbers with N_HI<1E15
cm^-2. We identify two groups of HI absorbers: strong absorbers with
N_HI=1E18-1E20 cm^-2 and weaker systems with N_HI=1E13-1E15 cm^-2. There are
none at intermediate N_HI.
  The strong absorbers may be a by-product of massive galaxy formation or could
instead represent material cooling behind the expanding bow-shock of the radio
jet, as simulated by Krause. New observations are required to discriminate
between these possibilities. We argue that the weaker absorbers with
N_HI=1E13-1E15 cm^-2 are part of the Lyman alpha forest, as their rate of
incidence is within a factor of 2-4 of that in the IGM at large. Such column
densities are consistent with models of a multi-phase proto-intracluster medium
at z>2.
