The conversations of two African heads of state have been eavesdropped by French police during a major investigation into alleged corruption by a French businessman. The transcripts of the phone-tapped conversations involving Mali's president Ibrahim Boubacar Keita, known as IBK, and Gabon's Ali Bongo reveal a vast system of gifts and favours apparently provided by controversial Corsican businessman Michel Tomi, who has been dubbed the “godfather to the godfathers”. As far as the judges investigating the case are concerned, the phone taps reveal corruption. And for French president François Hollande the content of the transcripts involving IBK will come as a devastating and embarrassing diplomatic blow. For much of Hollande's African policy has been based on the symbolic success of his old socialist friend IBK, who was voted in as president of Mali just months after Paris sent in troops to end an Islamic insurgency there. IBK's election was supposed to usher in a fresh start for Mali and a new era of French diplomacy in Africa. That narrative now looks to be in ruins. Fabrice Arfi, Ellen Salvi, Lénaïg Bredoux and Thomas Cantaloube report.