Mr Johnson, as foreign secretary and prime minister, has previously highlighted girls' education as a key to improving the health, wealth and security of the poorest countries. He once described it as the "Swiss army knife" of development, as getting girls to stay in education could avoid early marriage, improve their chances of getting a job and provide more income for children to be better fed.

"Matilda's story is particularly remarkable because she resisted what was expected of a black woman in the US South in the years after emancipation. She didn't get married. Instead, she had a decades-long common-law marriage with a white German-born man, with whom she had 14 children."

The "Rising Tide" exhibition shows the level of resistance, including violence, against women wanting to study at Cambridge with equal rights to men. This includes the remnants of a firework thrown by protesters in 1897 as they rioted against the revolutionary idea of women getting degrees.

Many young girls are expected to work rather than go to school. And many marry young, ending any chance of an education. UN figures indicate girls are more than twice as likely to lose out on education in conflict zones.