Time evolution of the separation between the two white dwarfs computed as the distance between the centres of mass of the material originating from both white dwarfs. We first shrank the binary system at a constant rate of 100 km/s for 108 s. We then evolved it for another 395 s self-consistently (i.e. the total angular momentum in the simulation was conserved). In this phase, mass transfer only shrinks it at a rate of ≈0.5 km/s. We then actively shrank it again at a rate of 10 km/s until it merged 166 s later. The cross denotes the time of explosion.