What really happened between Darcy and Wickham?

In Chapter Twelve, we learn that Darcy's father had indeed been very fond of Wickham and ensured that the boy received an excellent education. Before his death, Darcy's father asked Darcy to promote Wickham's professional advancement and provide him an income, stipulating that young Wickham become a clergyman (which was Wickham's professed aspiration). Wickham, however, had no actual desire to become a clergyman and after the elder Darcy's death, asked Mr. Darcy to give him the money to study law. Darcy gave Wickham 3,000 pounds, provided Wickham give up all claims to any further assistance. Wickham quickly abandoned his studies and squandered the money. Broke, he promised Mr. Darcy that he would become a clergyman in exchange for more money. When Darcy refused, Wickham was furious. Soon thereafter, Wickham deceived Georgiana Darcy into eloping with him, even though she was only fifteen. Luckily, Darcy caught wind of the plan and stopped his sister from following through. He is certain that Wickham was motivated both by Georgiana's fortune and his desire to punish Darcy.