Fiducial (maximum-a-posteriori) BEAGLE spectrum (green) and data (grey) around the Lyα transition. The dashed black line shows the effect of convolving the model spectrum with the prism LSF. The best-fit absorption profiles combining IGM and DLA absorption are shown by the dotted blue line and blue shading, assuming a fixed IGM neutral hydrogen fraction ${\overline{x}}_{\mathrm{H}\mathrm{I}}=1$. We tested a model with varying ${\overline{x}}_{\mathrm{H}\mathrm{I}}$, but this parameter is not well constrained, mainly because significant additional absorption is required to reconcile the profiles with the observed spectral break even with maximum IGM absorption (${\overline{x}}_{\mathrm{H}\mathrm{I}}=1$; see text for details).