Early evolution of the squashing factor Q. The panels display sign(B_z)log(Q) for a cutting plane at x = 5 Mm in purple (negative B_z) to orange (positive B_z) colours for t = 1.91 min, t = 3.43 min, t = 4.96 min, and t = 6.11 min. The magenta lines correspond to the flux rope field lines. The black ellipses indicate regions of intersection of the field lines with high Q values areas.