I'm guessing this one is a mayfly but don't know even the family to look in. It was about 25 mm long. Looks like a photo of an unidentified individual on page p 63 of Roger Farrow's Insects of SE Australia, 2016.
I think it is Monomachus antipodalis ... apparently a common species in Canberra. A match, do you think? https://canberra.naturemapr.org/Species/29907
I'd like to wait to hear from Kim before confirming it to species level.
Thanks Kerri-Lee. Certainly looks like that wasp. I'm not good at insects and there are so many species that look superficially similar, so I'm very grateful to have this help with ID.