Stromboceros delicatulus
In some references this genus is spelt with a penultimate u, Strombocerus. As far as I can tell that seems to be an error.
This individual came to light in my garden. It was identified using Adam Wright's key to genera (this being the only species in the genus in the UK) and checked against the information in www.sawflies.org.uk.
male Stromboceros delicatulus showing its wings, North Elmham (Norfolk, UK), 17th June 2022