Late light curve of GRB 100418A in X-rays and optical, where the contribution of the host galaxy has been removed. All the optical bands have been offset to the r′-band for clarity. Only data with S/N above 3, after host subtraction are plotted. At late times image subtraction techniques (thick dots) show that there is an excess of emission in the r′ and i′ bands, corresponding to a faint supernova. Solid lines correspond to the afterglow contribution in X-rays and optical. The dashed lines show the combined contribution of afterglow and supernova (for which we used SN 1998bw templates) scaled to match the late photometry. The dotted lines show the expected light curves for SN 1998bw at the redshift of GRB 100418A. Colour coding is equivalent to that of Fig. 1.