Darcy payed the fee that Wickham asked for in exchange for marrying Lydia.He did not tell Elizabeth that he had done so, and did it purely for Elizabeth despite what Wickham had done to his sister (georgiana).
In Jane Austen's novel "Pride and Prejudice," it is Mr. Darcy who finds Lydia Bennet and George Wickham after they elope. Mr. Darcy then arranges for their marriage to avoid scandal and uphold Lydia's reputation.
Mr. Darcy played a leading role in the search for Lydia and Wickham, as he was the one who ultimately found them and arranged for them to be married.
Lydia Bennet and George Wickham Charlotte Lucas and William Collins Jane Bennet and Charles Bingley Elizabeth Bennet and Fitzwilliam Darcy
Mr. Darcy found Lydia Bennet and George Wickham in London.
Lydia was supposed to keep Darcy's involvement in her wedding secret. Darcy had provided what was, in essence, Lydia's dowry, the money Wickham demanded to marry Lydia (though Lydia might have been unaware of the fact that Wickham would not have married her otherwise). This money was was used to buy Wickham an army commission and pay his debts. Darcy paid for the wedding, and attended it as best man.
Lydia's trip to Brighton, then came Lizzie's own trip.
Mr. Darcy gave George Wickham the money to marry Lydia in order to save the Bennet family's reputation and to ensure Lydia's well-being. Wickham had previously tried to elope with Lydia without intention of marrying her, which would have brought shame upon the family.
Ludia was fascinated and charmed by Mr Wickham and he was filled with desire and he convinced her to go away with him and get married without Mr and Mrs bennet's permission but Mr Darcy went after him and he caught them and convinced Mr Wickham to marry Lydia by paying him. So Mr Darcy was the reason of them getting married because he remembered what happened with his sister and Mr Wickham
Mr. Darcy believes it is his fault for the elopement because he knew what sort of man Mr. Wickham was, and he had to much pride to let the world know. If he had exposed Mr. Wickham's character, then the elopement would not have taken place.
Lydia and Wickham are found living together, unmarried and with no intention of marrying, in London. At first we are to believe Mr. Gardiner found them. Later, we find out it was Darcy.
Kitty and Lydia excitedly inform their mother, Mrs. Bennet, that Mr. Bingley is planning to host a ball at Netherfield Park. They also mention that Mr. Bingley arrived with his friend, Mr. Darcy, who is considered to be very wealthy and eligible.
The quote from "Pride and Prejudice" by Jane Austen is when Elizabeth Bennet tells Mr. Darcy about Lydia's behavior at the Netherfield ball: "She could have added, 'A young man, too, like you, whose very countenance may vouch for your being amiable.'"