While many are familiar with William Wilberforce, leader of the anti-slavery group in England known as the Clapham Sect, fewer know his pastor, John Venn of Clapham Parish. Venn is one of the better-kept secrets behind Wilberforce's success.

Here's the back story.

On most weekends for many years, Wilberforce and his fellow abolitionists met in Clapham, a village outside of London. There they developed their strategies for, as they put it, "reforming the manners and morals of all England."

But on Sunday mornings, Wilberforce and the others always paused to worship at John Venn's church. As the years passed, John Venn's preaching and pastoral wisdom influenced them in no small way.

"The whole Clapham sect looked up to (John Venn) as their pastor and guide," writes Marcus Loane, "and he was thus intimately linked with their thoughts and plans … both as a friend in their homes and as a pastor in his pulpit."

Venn, Loane continues, "was a master in the art of advice when called upon to speak ...