Nigeria's former oil minister Diezani Alison-Madueke was arrested in London on Friday, a source from Nigeria's presidency circle and another with links to her family said. Alison-Madueke was minister from 2010 until May 2015 under former president Goodluck Jonathan, who was defeated by Muhammadu Buhari at the polls in March. Buhari took office in May promising to root out corruption in Africa's most populous country, where few benefit from the OPEC member's enormous energy resources. A police spokesman in London said he had no record of such an arrest. The National Crime Agency did no