A characterisation of octahedrality in Lipschitz-free spaces
  We characterise the octahedrality of Lipschitz-free space norm in terms of a new geometric property of the underlying metric space. We study the metric spaces with and without this property. Quite surprisingly, metric spaces without this property cannot embed isometrically into $\ell_1$ and similar Banach spaces. 
Anton\'in Proch\'azka and Abraham Rueda Zoca
math.FA