Published online by Cambridge University Press: 20 November 2018
We prove that a Banach space $X$ has the Schur property if and only if every $X$-valued weakly differentiable function is Fréchet differentiable. We give a general result on the Fréchet differentiability of $f\,\circ \,T$, where $f$ is a Lipschitz function and $T$ is a compact linear operator. Finally we study, using in particular a smooth variational principle, the differentiability of the semi norm ${{\left\| {} \right\|}_{\text{lip}}}$ on various spaces of Lipschitz functions.