Entering the British film industry as an assistant cameraman while still a teenager, Day became a director of photography in the '40s. He began directing in the mid '50s, and is remembered most fondly for his comedies The Green Man with Alastair Sim and Two-Way Stretch with Peter Sellers, and for his horror tales with Boris Karloff, Grip of the Strangler (aka The Haunted Strangler) and Corridors of Blood. He came to specialize in adventure films in the '60s, including She and several Tarzan movies. He turned his efforts to television in the '70s and '80s, amassing an impressive list of credits that included shows like Dallas, Kojak and Matlock. Day died in 2017, at age 94.