This is an introduced plant from Southern europe which occasionally escapes into the wild from gardens. Here it was in dense shade hence the strange colouration but well naturalised amongst Petasites hybridus (Butterbur) and Allium ursinum (Ramsons). There are supposed to be two sub species which Stace is very doubtful about as intermediates occur in gardens. If the sub species do exist then this one is ssp bulgaricum being the paler flowered with greenish tepals.