My sister's boyfriend found this large wasp a few years ago in Kent - apparently it was quite aggressive. I've shown it next to a common wasp and hornet for a size comparison - does anyone know what species it is?
It is a scoliid wasp, http://en.wikipedia.org/wiki/Scoliidae, but from what I can tell they are not indigenous to the British Isles. So, either this one was imported from, for example, France or it migrated in from the South, perhaps after strong winds. Worthwhile to get this specimenexamined and properly recorded by a British aculeate specialist. It might be Megascolia maculata.