Constraints in the Ω_m–H₀ plane. Points show samples from the Planck-only posterior, coloured by the corresponding value of the spectral index n_s. The contours (68% and 95%) show the improved constraint from Planck+lensing+WP. The degeneracy direction is significantly shortened by including WP, but the well-constrained direction of constant Ω_mh³ (set by the acoustic scale), is determined almost equally accurately from Planck alone.