The South West of France's answer to the Angel of the North

Lorraine and Neville Dowson from Sunderland have found this interesting stone in their grange and wondered what purpose it used to serve. Whatever it is, we have one the same and I grow a  climbing plant through the middle. I thought it might be a toilet seat for a privy but Malc pooh, poohed the idea. Any ideas to mail@bromlea .com to be passed on to Lorraine and Neville and TAG readers of course. Bernadette Curato from Espinas who helps to organise the Fenaison may know some old agriculteur who knows the answer.
Celia Berry says  it is a roman toilet. She has just watched a TV programme where the exact stone was being talked about and it was a toilet.