Same as in the bottom panel of Figure 3, but focusing here on later times, i.e. beyond the disc’s initial slow collisional evolution (Figure 1). The rate of change of the DF is estimated through simple time differences, as indicated in each panel. In each panel, the colours are rescaled to the minimum and maximum value of the local relaxation rate in that panel, as indicated therein. For simplicity, even at late times, actions remain evaluated within the disc’s initial unperturbed axisymmetric potential from Equation (1).