A classical ensemble is employed to investigate double ionization of helium for laser wavelength 390 nm and intensity 1.1PW/cm2, below the threshold for recollision impact ionization. Significant numbers of trajectories that lead to electron energy above 2Up are shown to be present and to feature a time delay between recollision and final ionization. Processes through which nuclear and laser forces combine to give an electron final energy above 2Up are identified.