Relaxation rate, ∂F/∂t, in (J_r, cos I) as in Fig. 9, but here from the NR theory (see Appendix H.2 for details). While the in-plane isotropisation and the smoothing of the inclination distribution is recovered, finer details disagree. Here, the amount of relaxation was estimated using finite differentiation using separately regions with positive or negative cos I In effect, this removes the δ′(cos I) singularity in cos I​ = ​0, as discussed in Appendix I. Importantly, the removal of this singularity does not affect the prediction away from cos I = 0. In addition, because this singularity is diluted in N-body measurements – as discussed in Fig. 9 – we do not represent the NR prediction here.