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 \simeq 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 galaxies , 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 } \approx 1.5 –2 .
This is in agreement with observations of other high redshift clusters , but in disagreement with field galaxies at similar redshifts .
The shape of the luminosity function at high redshift , after correcting for passive evolution , is not significantly different from that of the Coma cluster , again consistent with passive evolution .