The derangements subgroup in a finite permutation group and the Frobenius–Wielandt theorem

It is known that if the derangements subgroup of a transitive non-regular permutation group is a proper subgroup, then it is a Frobenius–Wielandt kernel, and, conversely, minimal Frobenius–Wielandt kernels are proper derangements subgroups. We present here a short survey of the literature on this topic, and we show that, although there are no restrictions on the structure of the p-groups appearing as Frobenius–Wielandt complements, a p-group appears as a one-point stabiliser in a transitive non-regular permutation group with a proper derangements subgroup if and only if it satisfies a certain group-theoretic condition.