Gilling left a job in England with an oil company at the age of 17 and spent a period in Hollywood, working in the film industry some of the time, before returning to England in 1933.[1] He entered the British film industry immediately as an editor and assistant director, starting with Father O'Flynn. He served in the Royal Navy in the Second World War.
After the war, Gilling wrote the script for Black Memory (1947), and made his directing debut with Escape from Broadmoor (1948). Gilling also produced and directed Old Mother Riley Meets the Vampire (a.k.a. Vampire Over London / My Son the Vampire) in 1952. Gilling continued through the 1950s making second features such as The Voice of Merrill for Monty Berman's Tempean Films and entered television directing in several British series that received international distribution such as Douglas Fairbanks, Jr., Presents and Gideon's Way, as well as Monty Berman's The Saint, The Champions, and Department S. Of his films for Tempean, the film historians Steve Chibnall and Brian McFarlane say: "Gilling shows in all of them a capacity for establishing the premises of his plots economically and evocatively, for developing them with clarity and speed, for giving competent players a chance to invest their characters with a feeling and detail that go beyond stereotype, and for making deft use of limited locations and settings."[1]
Following a final round of work in British television Gilling relocated to Spain, where he came out of retirement in 1975 to make Cross of the Devil, his final film.