The buzz about fintech in Lagos, the commercial capital of Nigeria, is so loud that even those without access to the internet cannot miss it. Flashing billboards advertising Kuda, a digital bank, loom over traffic jams, and signs for Paga, a mobile-payments company, adorn thousands of corner shops. Investment has been flowing in, too. In March Flutterwave, a digital-payments firm, raised $170m, making it Africa’s latest unicorn (ie, a startup valued at more than $1bn).