My friend Effa Okupa, who has died aged 82, was a professor of law whose speciality was African customary law, especially of matrilineal tribes.

She was a visiting professor at the University of Namibia (Unam) and was instrumental in establishing the law faculty there. In 2006 she published a book, Carrying the Sun on Our Backs: Unfolding German Colonialism in Namibia from Caprivi to Kasikili.

Born in Esan, in Edo State, Nigeria, to Dominic, a nurse, and Christiana Okupa, she received her secondary education at Queen of Apostles college, Kakuri, Kaduna, before coming to the UK to train as a teacher – first, in 1957, at Bedford College of Physical Education, and then at Homerton College in Cambridge, where she lodged with the anthropologists Jack and Esther Goody, establishing a lifelong relationship.

She began teaching in 1961 at schools in London. From 1971 to 1988 she taught at Copeland school in Wembley, then embarked upon a London external law degree, having completed an Open University degree in 1979. In the second year of the course she elected to study Roman law, then a rather unusual choice. I teach Roman law at University College London, and Effa engaged me to teach her for an hour each fortnight after school. Our conversations were not always law-related: Effa was very concerned at the effect that Margaret Thatcher’s policies were having on secondary education, though she tempered her criticism in view of the significance of Thatcher becoming the first female prime minister.

Having passed the London external LLB in 1989, Effa took her master’s at UCL (1990), then her PhD at what is now Soas University of London (1996). Her fieldwork took her to Namibia, where she worked among the traditional communities, but especially the marginalised Ovahimba. From 1998 to 2009 she was visiting senior lecturer in customary law at Unam, then visiting professor of customary law from 2010, latterly emeritus.

Her base remained London, and from 2000 she joined the Sacred Law group, an informal collection of historians and lawyers interested in questions associated with religious laws, meeting at Soas.

Effa’s interest in the legal and social features of matrilineal societies intensified and, late in life, she organised a research trip to a remote part of China to study the matrilineal system there. She was working on a book on the subject at the time of her death.

Effa encouraged her brightest Unam law students to study in London for a few months, despite the formidable hurdles. She arranged for the academic lawyers Dame Hazel Genn and Stephen Guest, and the philosopher Joe Wolff, to work with her students. This stimulus helped one of them win a Rhodes scholarship to Oxford.

Her strong Catholicism was anchored in family tradition (a relative was a cardinal). Hardest to convey is her combination of strength of character and affectionate charm.

Effa is survived by her son, Kwesi, from a marriage that ended in divorce.