(Editor's note: The movie Amazing Grace tells the story of the end of the slave trade in the United Kingdom very well, but there is so much that can't be squeezed into two hours, such as this: the effect of a single letter from a humble pastor to an embattled and exhausted friend. The pastor was John Newton, one-time slave trader himself who, saved by the grace of Jesus Christ, penned the simple hymn that is now the world's favorite. And the recipient of that letter was his young friend, abolitionist-campaigner William Wilberforce, who was ready to quit. This article is featured in our sister publication, Christian History & Biography.)

On the evening of March 15, 1796, the streets adjacent to the Opera House of London thronged with carriages carrying the wealthy and powerful. Excited conversation buzzed beneath wrought-iron streetlamps. It was the premiere of the opera season. Vignoni, the noted Italian singer, was the lead in a new comic opera, I Dui Gobi—his first London performance ...