At first glance I thought this big brute was a hoverfly, ’cause I know there are some very large hoverflies, but one look at those eyes told me otherwise. Meet Tachina grossa, the largest Tachnid fly in Britain and Europe.
As you can see, it feeds on pollen and nectar and, though it’s harmless to us humans, it’s no friend of moths. The female Tachina grossa lays her eggs on living larvae, in particular the large hairy caterpillars of the Oak eggar moth and the Fox moth. The fly larvae eat the caterpillars from the inside, eventually but not immediately killing them.
So, it may look kind of cute in the photograph below but I’m just glad I’m not a large hairy caterpillar.