A group of these plants were growing on the riverbank and on a rubbly bank at the side of the riverside path behind industrial units. It looks like a relative of water avens but doesn’t have the drooping flowerheads of that species. Most of the flowers were yellowish green but some plants had flowers midway down the stem with magenta petals. A garden escape?
Next day we spotted this plant amongst the ferns at Brodsworth Hall and Gardens. It’s a Heuchera, a member of the saxifrage family from North America, so definitely a garden escape.