I first spotted this Digger Wasp as it flew past me carrying a Bluebottle. It landed and there was a bit of a struggle before the Bluebottle succumbed.
Digger Wasps get their name from their habit of digging tunnels into soft sandy soil, then catching and paralysing other flies, and transporting them back to the tunnels. They then lay their eggs in the unfortunate flies and their larvae eat them.
I think this Digger Wasp is Mellinus arvensis.