Dictamnus albus var. purpureus
What a long Latin name for a plant we commonly know as gas plant. The flowers give off a flammable gas but it has a very unpleasant odour if the gardener is to light it on fire. I can only imagine who fooled around initially to discover this interesting aspect about the plant.
Dictamnus slowly forms an upright clump with these pretty flowers (just as nice with the white form) and attractive star-shaped seed pods.
One must be very careful gardening around this plant on warm sunny days and avoid contact with the leaves. I can attest to the chemical burn it can create as a couple of years ago I had both my arms blister and it took the longest time to figure out which plant had done this and a couple of months for the mess to clear up.
It's still worth having though and flowers in June to July in most soil types.