  K band observations of the galaxy populations of three high redshift
(z=0.8-1.0), X-ray selected, massive clusters are presented. The observations
reach a depth of K=21.5, corresponding to K*+3.5 mag. The evolution of the
galaxy properties are discussed in terms of their K band luminosity functions
and the K band Hubble diagram of brightest cluster galaxies.
  The bulk of the galaxy luminosities, as characterised by the parameter K*
from the Schechter (1976) function, are found to be consistent with passive
evolution with a redshift of formation of z_f~1.5-2. This is consistent with
observations of other high redshift clusters, but may be in disagreement with
galaxies in the field at similar redshifts. A good match to the shape of the
Coma cluster luminosity function is found by simply dimming the high redshift
luminosity function by an amount consistent with passive evolution. The
evolution of the cumulative fraction of K band light as a function of
luminosity shows no evidence of merger activity in the brighter galaxies.
  The evolution of the brightest cluster galaxies (BCGs) is tested by their K
band Hubble diagram and by the fraction of K band cluster light in the BCGs.
The evolution observed is consistent with recent previous observations although
the scatter in the Hubble diagram allows for a range of evolutionary histories.
The fraction of cluster light contained in the BCGs is not smaller than that in
Coma, suggesting that they are already very massive with no need to hypothesise
significant mergers in their futures.
