Bayesian movable knot reconstructions of the primordial power spectrum using Planck TT data. The plots indicate our knowledge of the PPS for a given number of knots. The number of internal knots N_int increases (left to right and top to bottom) from 0 to 8. For each k-slice, equal colours have equal probabilities. The colour scale is chosen so that darker regions correspond to lower-σ confidence intervals. 1σ and 2σ confidence intervals are also indicated (black curves). The upper horizontal axes give the approximate corresponding multipoles via ℓ ≈ kD_rec, where D_rec is the comoving distance to recombination.