  In this note we consider a $p$-isometrisability property of discrete groups.
If $p=2$ this property is equivalent to unitarisability. We prove that any
group containing a non-abelian free subgroup is not $p$-isometrisable for any
$p\in (1, \infty)$. We also discuss some open questions and possible relations
of $p$-isometrisability with the recently introduced Littlewood exponent ${\rm
Lit}(\Gamma)$.
