Leonard was an American terrorist, drug dealer, and leader of a crime syndicate in London. He had influence over Adrian Mulheron, one of his drug runners, swaying him time and time again to keep on the job. He was murdered by Roz.
Leonard was an organized crime boss moving forward with a big operation to setup Adrian for a terrorist attack in London in order to get him out of his way. Leonard convinced Adrian to go through with running what he thought to be drugs through customs at the airport. However, Roz showed up to intervene, ultimately killing Leonard.