Billy

Billy was a British citizen living on the streets of London in the mid-nineteenth century.

In 1868, Billy was contacted by Dr. Wilburn, who paid him a small amount of money to keep tabs on the Asquith residence, informing him of everything that went on there. This information was then passed on to Thaddeus the Great, who used it to convince Janice Asquith that he was a true spiritualist, allowing him to swindle her into marrying Everett Boyd.

Reference

 * Assassin's Creed: Syndicate - The Dreadful Crimes