  Odell and Schlumprecht solved the distortion problem by proving that the
classic sequence spaces $\ell_p$ for $1<p<\infty$ admit an inevitable
biorthogonal system. In particular, these spaces are arbitrarily distortable.
Later, Maurey extended the result to asymptotic $\ell_p$-spaces while
Tomczak-Jaegermann did likewise for the Schatten classes. We observe that the
Kalton-Peck spaces $Z_p$ for $1<p<\infty$ admit an inevitable biorthogonal
system. Therefore, we may add this classic family to the list of arbitrarily
distortable spaces.
