EVANS OMONDI JACK was born 60 years ago in a labour camp in Nairobi, Kenya’s capital, a precursor to a present-day slum known as Mukuru kwa Reuben. It was named after a British veteran of the second world war who got the land from colonial authorities. After Kenya’s independence in 1964, ownership passed to the state and was eventually parcelled out, often in return for political favours, to wealthy or well-connected individuals. Since then Mr Omondi has been forcibly evicted from his birthplace on four occasions. Each time he returned and rebuilt.

Descendants of the original Reuben work-camp residents, augmented by new arrivals, number more than 100,000 today. They make up part of Nairobi’s 2.5m slum dwellers, some 90% of whom have no rights to the land on which they live. Mr Omondi, with the help of a local NGO, Muungano wa Wanavijiji, has launched a legal bid to unravel the area’s murky ownership and expose dodgy titles. His petition names some of Kenya’s most powerful people.

Paul Muite, the plaintiffs’ lawyer, says a coming court battle could establish an “explosive precedent” in a city where two-thirds of the population lives on less than 2% of the land, typically in ten-foot by ten-foot shacks. Under Kenyan law the land at issue should have been sold at public auction and then developed within two years or handed back to the state.

The petitioners argue that in Mukuru both laws were ignored. Some owners held on to the land for decades, using it as collateral for loans; others sold it on the sly. Undeveloped land was often rented by new arrivals, for whom developers, locally known as “slumlords”, built shanties.

Nairobi is now home to nearly 4m people—and some of the sharpest inequalities in Africa. Leafy suburbs like Muthaiga, near the UN’s regional head office, have one household per acre compared with an average of 318 in slum areas.

Shantytowns are the norm in Africa’s big cities. World Bank research suggests that legal tangles over land tenure hobble efforts to upgrade them. Only where residents have secure tenure will they invest in their homes. The Mukuru petition, if it succeeds, could make a huge difference.