Shagari’s regime (1979-1983), incurred Buhari’s wrath when it decided to investigate the US$2.8 billion that disappeared from the Midland Bank, London account of the Nigerian National Petroleum Cooperation, (NNPC), during General Obasanjo’s era as military head of state that preceded Shagari’s. Dr. Olusola Saraki, Turaki of Ilorin, was the majority party leader of the Senate at the time and he headed the Senate Committee set up to trace the stolen money after some three years of clamour for such an investigation by members of the civil society. The money was traced to the Midland Bank London branch fixed account of Obasanjo’s appointee as military head of the Nigerian National Petroleum Company. The Committee’s report was presented to the Senate during the tail end of Shagari’s regime in 1983, so the House decided to deal with the matter and expose the rogue military head of the NNPC soon after the 1983 general elections.
http://saharareporters.com/2010/04/30/all-nigerian-coup-generals-were-rogues%E2%80%A6and-general-muhammadu-buhari-was-no-exception