Mock lensed kinematic data of the source galaxy of RX J1131−1231 for the composite mass model (left panel), our prediction obtained by modelling the data with a power law profile (central panel) and the normalised residuals (right panel). The data are binned to obtain a signal-to-noise in each bin of 30, for a total of 22 bins. The pixel resolution of the kinematic maps is 0.1″. The masked black region is the region in the image plane which has no correspondence on the source plane. The yellow cross marks the lens centroid position.