Fake.
However the story behind it is probably more interesting than the photo. 'State of the art' equipment, including a pair of scissors and air-brushing (for the propeller) were used. Created by Cyril Peckham, FRPS;Hon CRAeS of the Isle of Wright, in March 1940 while editor of the house magazine, General Aircraft Ltd. He described the event in his article, as good luck, while airborne on a photographic sortie coming across the Spitfire completing a circuit with a rigger clinging to the rear fuselage.
The photo was so believed at the time that the Press offered him 5,000 pounds for the "scoop" photo, for the rights to distribute it world wide.
At the time he explained that he couldn't accept the offer because of his official position and "censorship"!
He 'came clean' on the photo in a talkback column in a May 1979 issue of AIR International.