A US businessman backed by former CIA and state department officials says he has secured a vast tract of fertile land in south Sudan from the family of a notorious warlord, in post-colonial Africa’s biggest private land deal.

Philippe Heilberg, a former Wall Street banker and chairman of New York-based Jarch Capital, told the Financial Times he had gained leasehold rights to 400,000 hectares of land – an area the size of Dubai – by taking a majority stake in a company controlled by the son of Paulino Matip.