A rust gall on the alternate host, Anemone.  The under surfaces of the leaves are covered in a rash of small aecia with a white peridium.  The petiole of the plant is elongated so that it stands above the surrounding unaffected plants.  The leaflets are narrower and often paler.

The primary hosts bearing uredinia and telia are various species in the Rosaceae; in Redfern and Shirley 2023 (British Plant Galls), Rowan is the only species listed as the primary host.

host/gall

Photograph the gall on the host plant; note the host plant species in your comments

Woodlands, on Anemone nemorosa (aecial stage).  Primary host is Rowan.

Aecial stage in Spring

Rare (Redfern and Shirley 2023)

Rare.  The 2026 Ratby Burroughs record is believed to be the first in VC55.