Roger J. Cockram

Roger Cockram. He did domestic ware in the late 70's, but it much more famous for his decorative dishes. A North Devon pottery

I don't think so. Roger Cockram has been a professional potter nearly all his life, and the Clover Leaf mark you are thinking of is one he used when he was at the height of his professional work from 1986 onwards
The mark does not look quite crisp enough. Moreover, I am sorry to say the piece just not look in any way good enough. He really is excellent potter, and I have had several pieces of his work. Possibly by a student, which like most potters he probably had.