FOR a government that spent three years rebuilding its case to international creditors, the timing could not have cut deeper. On May 15, S&P Global Ratings lifted Nigeria's long-term sovereign credit rating from 'B-' to 'B', the country's first upgrade in fourteen years and the clearest external validation yet of President Bola Tinubu's reform programme - exchange-rate liberalisation, subsidy removal and tighter capture of petroleum revenue. Six weeks later, Nigerians learned that a man calling himself Prince Adeniyi Adeyemi Matthew had spent roughly a year running an entirely invented federal agency out of an office inside the Federal Secretariat Complex…