  Very deep imaging data of three optically luminous radio-loud quasars with
redshifts between z=0.9 and z=1.36 are presented. The data are complete for
galaxies down to R=26. There is no evidence for excess numbers of galaxies
around the quasars; foreground galaxy clusters are excluded by the data as well
as clusters with richness classes greater than 1 associated with the quasars.
We find clear evidence for gravitational lensing for two quasars. It is further
shown that due to the high surface density of galaxies all distant (z>1)
objects are moderately affected by gravitational lensing; the amplification
factors are estimated to be in the range 1.1-1.5.
