A large leafhopper, 6.5 to 8 mm, on oak, with a broad head. The forewings range from green to pale brown and the vertex, pronotum and scutellum are spotted and mottled with brown. 

Iassus scutellaris on Elm

Good photographs taken in the field, or from a specimen; you must note the species of tree on which it was photographed/collected

Associated with Oak.

Adult: June to October.

Widespread and common in Britain. (ref.: UK Auchenorrhyncha checklist 2021, on British Bugs website)

Fairly frequent in Leicestershire and Rutland.

https://www.britishbugs.org.uk/homoptera/Cicadellidae/Iassus_lanio.html