Synchronising primitive groups of diagonal type exist

Every synchronising permutation group is primitive and of one of three types: affine, almost simple, or diagonal. We exhibit the first known example of a synchronising diagonal type group. More precisely, we show that $mathrm{PSL}(2,q)times mathrm{PSL}(2,q)$ acting in its diagonal action on $mathrm{PSL}(2,q)$ is separating, and hence synchronising, for $q=13$ and $q=17$. Furthermore, we show that such groups are non-spreading for all prime powers $q$.