In 1754 the newly-arrived governor of Angola, António Alvares da Cunha, announced to the court in Lisbon that, inspired by plans his uncle had made in 1725, he had decided to revive the old attempt to find a way overland to link Angola and Mozambique. He was initiating this enterprise by sending, at his own expense, an expedition to the fair of Cassange, the farthest known point eastwards of Luanda, to gather information about the lands between Angola and Mozambique. The governor's envoy was Manoel Correia Leitão— an experienced trader, but one who had never been to Cassange— accompanied by a pilot, António Roiz Grizante, whose task was to fix the latitude of Cassange.
A suspicious reader could conclude with the subsequent governor António de Vasconcelos, that this venture was a slave trading expedition by Leitão to recover some debts. But it was financed by the governor and one suspects that the whole enterprise was in fact a joint business venture, disguised as an exploration, because governors were forbidden to trade. Be that as it may, the reaction from Lisbon to this news was unexpected. The governor was ordered to abandon his plans and to recall his envoys because this enterprise was too “delicate.” Knowledge about it was to be shrouded in absolute secrecy and a report about this was to be treated as top-secret. Whereupon the governor recalled Leitão.