Mark Doyle is an Irish loan shark operating in Boston, and is played by Irish-born actor Alan Smyth. He appears in the season two episode The Bottle Job.
The son of major Belfast loan shark Tim Doyle, who was once active in the Irish Republican Army, Mark persuaded his father that he could expand the business into the US, and operates out of Boston. He deals in cash, and uses two enforcers named Liam to collect for him, with each bill he collects carefully marked. Doyle makes loans to families and small business that can't otherwise get them because of the credit crunch, believing he provides a "service" to the community.
Doyle comes to the Leverage team's attention when he attempts to collect on a note signed by John McRory at his wake, giving his daughter Cora two hours to pay back $15,000 or lose the pub. Nate calls in Tara, who Doyle hasn't seen, to get some background. Doyle tells Tara that he works for the family business, which he describes as a bank based in Belfast, explaining that he is VP in charge of overseas expansion. Doyle is determined to prove to his father that he can run a branch of the family business on his own, which Tara realizes is his weakness. The team steps in, and eventually takes all of Doyle's money in a combination poker and wire scam, saving the pub for Cora.