It is explicitly shown that part of the C-metric space-time inside the black hole
horizon may be interpreted as the interaction region of two colliding plane waves
with aligned linear polarization, provided the rotational coordinate is replaced by
a linear one. This is a one-parameter generalization of the degenerate Ferrari–
Ibanez solution in which the focussing singularity is a Cauchy horizon rather than
a curvature singularity.