evidence: Abyei, a fist of oil-rich land on the border between Sudan and South Sudan, is violently contested. Abyei is a tormented piece of land, locked on the border between Sudan and South Sudan. [...] Abyei is also ethnically contested. It is claimed by a southern sub-tribe – the Ngok-Dinka – who raise livestock and live inside the box. They held a unilateral referendum in 2013, voting to join South Sudan, but this has never been recognised.