Thanks Sue and antiquerose123.
I've had another go with graphite and talc...IT WORKS!
I'm fairly sure it is still LeD but i suppose it could be L & D Or LcD .
Sue, I had thought about the Lowerdown possibility as it has some Leach similarities. However, I've got some Lowerdown with a very different marks and haven't seen anything like it on the Studio Pottery site.
Maybe someone will be able to have more ideas with the new picture.

Thanks again,
David