Studio bowl, swirly porcelain?,B inside D mark

Studio bowl, swirly porcelain?,B inside D mark
I’m unsure if this is porcelain.
Mark is a bit like Ben Daniel in book but not the same. And not much of his work online to see.
The swirls in this are perhaps coloured clays, kind of marbling or swirling glazes. I don’t know enough about how something like this is made.
Thanks

Not Ben Daniel’s usual mark

Probably porcelain. It is made by taking three pieces of clay, two coloured and one white, patting them together, and then using this to throw a bowl on a potter's wheel. The actions of throwing create the patterns which are usually partly concealed by the slurry produced naturally when throwing. The outside has been turned when the pot is leather-hard, revealing the clear patterns. As to who made it - I have no idea!

Often known as "agate" ware. Rather like Alton Towers pottery.

Thank you Lisa & Denby, that’s really helpful.