Slice of the Lagrangian halo regions of the two “baseline” simulations (left and right panels, respectively). These simulations only differ in sub-resolution perturbations to the initial conditions and their level of agreement sets a baseline for the desired accuracy of our models. The colours employed for both panels represent the mass of the halo associated with each particle for the different Lagrangian halo patches. Circled regions highlight Lagrangian patches whose associated mass significantly changes between the two simulations.