William Folorunso Kumuyi was born on 6 June 1941 in Erin-Ijesa, Osun State, to an Anglican family. He read mathematics at the University of Ibadan, then took a postgraduate education degree at Cambridge, and returned to lecture at the University of Lagos.
In 1964 he was expelled from the Anglican communion for what his own account calls "an encounter with holiness teaching" during a revival led by Apostolic Faith minister T.L. Osborn's Nigerian associate. He joined the Apostolic Faith Church and began teaching a Bible-study circle for university students.
On 20 August 1973, fifteen students met in his Akoka bungalow near the University of Lagos campus for what he called the Deeper Christian Life Bible Study. By 1975 the meeting had grown to over a thousand, spilling out of the house and into rented halls. By 1982 the group had formally constituted itself as the Deeper Life Bible Church, with Kumuyi as General Superintendent.
"Deeper Life's early identity was severe: no jewellery, no trousers for women, no television for a period in the 1980s, and an insistence on second-blessing sanctification borrowed from the Wesleyan-Holiness tradition. Its Monday Bible-study manuals were mimeographed, then printed, and distributed to hundreds of thousands of homes across Nigeria — the country's first mass-produced discipleship curriculum."
By 1988 the Gbagada headquarters in Lagos was drawing over 70,000 worshippers on Sundays — at the time reportedly the single largest congregation in the world. The church's Retreat Camp on the Lagos–Ibadan Expressway, opened in the 1990s, hosts periodic crusades of over a million attendees.
Kumuyi remains General Superintendent into his eighties, still lecturing from the pulpit with a mathematician's blackboard cadence. Deeper Life now claims a presence in more than 100 countries and over 800,000 baptised members in Nigeria alone — an entirely indigenous, non-imported movement that reshaped Nigerian evangelicalism.