From
History Around Hull

What inspired Wilberforce to fight for the abolition of slavery?

I think it was his Christian belief and humanitarian interests. There was a gentleman called Captain Middleton who invited him to a dinner where a lot of abolitionists were dining there, and they actually approached Wilberforce to tell him about the awful conditions that the slaves were transported and sold. He decided there and then that he wanted to fight for the abolition of slavery in Parliament.