The aphid Tetraneura ulmi causes a fig like gall to be formed on certain species of elm. This is a quite large, solitary, upright, pouch like gall on the upper surface of the leaf. The gall is more often seen than the adult aphid.

Gall Adult

Anywhere that the host species - English Elm, Wych Elm or Small-leaved Elm are present

Fairly frequent and widespread in much of Britain.

Fairly frequent  in Leicestershire and Rutland.

https://influentialpoints.com/Gallery/Tetraneura_ulmi_Elm-grass_root_aphid.htm