Wall Pepper.

That is one of the names for Biting Stonecrop (Sedum acre) although in some country districts it was known as “ welcome-home-husband-though-never-so-drunk”. The longest name for any English wild flower. It has a hot bitter taste. It grows in many places including on rooftops. Here it is growing on the limestone pavement in Gait Barrows NNR.

In the top right are the white flowers of Limestone Bedstraw.