John Luther asks his partner to call "Detective Munch, in New York. He works in the Special Victims Unit." This is a reference to Law & Order: Special Victims Unit (1999), which stars Richard Belzer as Detective John Munch, a character who has appeared on American television for over 15 years. The character first appeared as a regular in NBC's Homicide: Life on the Street (1993) and later carried over to become a regular on the equally long-running SVU.
Ross McCall's character as the vicious American might be a call back to his recurring role as antagonist on White Collar (2009).