The "L.C.C." on the side of the ambulance stand for "London County Council".
Two of the film's characters, a pair of American police officials visiting Scotland Yard, observe that Michael Lanyard had no children and was never even married. However, in an earlier entry of the Lone Wolf series, The Lone Wolf Spy Hunt (1939), Lanyard is presented as a widower with a young school-aged daughter named Patricia.