Not a common find between the tides and all the ones I've found have been found under stones and rocks, and these are rarely open showing tentacles. Images show this, and importantly, show how different this anemone looks when closed.
Species photographed on the lowershore at Spit Point, Par; and at Carnsew Pool near Hayle, Cornwall.
Scientific and European Names:
Sagartia troglodytes, Mud sagartia, Slibanemoon, Sagartie de vase(s), Schlamm-Sagartia.