  In this work we investigate the gravitationally lensed system B1422+231.
High--quality VLBI image positions, fluxes and shapes as well as an optical HST
lens galaxy position are used. First, two simple and smooth models for the lens
galaxy are applied to fit observed image positions and fluxes; no even remotely
acceptable model was found. Such models also do not accurately reproduce the
image shapes. In order to fit the data successfully, mass substructure has to
be added to the lens, and its level is estimated. To explore expectations about
the level of substructure in galaxies and its influence on strong lensing,
N-body simulation results of a model galaxy are employed. By using the mass
distribution of this model galaxy as a lens, synthetic data sets of different
four image system configurations are generated and simple lens models are again
applied to fit them. The difficulties in fitting these lens systems turn out to
be similar to the case of some real gravitationally lensed systems, thus
possibly providing evidence for the presence and strong influence of
substructure in the primary lens galaxy.
