I visited Kirkby Moor last week with my parents and spent a lovely afternoon looking for plant galls and other things. I was checking out an oak tree for galls when I spotted a parasitic wasp on a leaf mine. This was fascinating to watch and I had a go at photographing the behaviour.
The larva is Tischeria ekebladella, a moth. I doubt I'll be able to put a name to the wasp, though (and I'm now regretting not taking the leaf home to have a go at raising the parasite for ID).