"As soon as we got here, I loved it," she says.

It comes from the Chokwe, Luchazi and Luvale people, who live in the borderlands of Angola, the Democratic Republic of Congo and Yonga's own north-western region of Zambia.Geometric patterns were made in the sand, on cloth and on people's bodies. Or carved into furniture, wooden masks used in the Makishi ancestral masquerade - and a wooden box used to store tools when people were out hunting.

The patterns and symbols carry mathematical principles, references to the cosmos, messages about nature and the environment - as well as instructions on community life.The original custodians and teachers of Sona were women - and there are still community elders alive who remember how it works.They are a huge source of knowledge for Yonga's ongoing corroboration of research done on Sona by scholars like Marcus Matthe and Paulus Gerdes.

"Sona's been one of the most popular social media posts - with people expressing surprise and huge excitement, exclaiming: 'Like, what, what? How is this possible?'"The Queens in Code: Symbols of Women's Power post includes a photograph of a woman from the Tonga community in southern Zambia.

She has her hands on a mealie grinder, a stone used to grind grain.

Researchers from the Women's History Museum of Zambia discovered during a field trip that the grinding stone was more than just a kitchen tool."It has taken 50 years for [the exhibition] to be revisited and understood for what it was really trying to say," says the 73-year-old who lives near King's Lynn, Norfolk.

Tutti modelled for pornographic magazines in her work as a performance artist and pages from these publications featured in Prostitution, but were hidden away in a back room.She says she "infiltrated" the porn industry to turn the tables on the consumers of these magazines and subvert the male gaze - the watcher now being watched.

"It's my point of view. It was my action," she says in the grounds of Castle Acre Priory, Norfolk.She wanted the exhibition to "bring [porn] into a different kind of viewpoint and interpretation" and to "empower women to think that [the porn industry] is something we have to discuss, regarding how you think of it, as either subverting it or going along [with it]".