Despite the oft-repeated assertion, this was not Britain's first Talkie. That honour goes to the Edgar Wallace adaptation, The Clue of the New Pin, although it's obvious from the longevity of Alfred Hitchcock's picture which was the superior. Adapted from a play by Charles Bennett, Blackmail was originally filmed as a silent and then wholly reshot with sound when recording technology became available. Both the mute and the talking versions were released, as few British cinemas had been wired for sound, and there are visual differences between the two. However, it was the spectacle of the cast speaking that drew the curious and gave Hitch his biggest box-office hit to date.
Dispensing with the services of Eliot Stannard, who had scripted eight of his nine previous features, Hitchcock co-opted Benn Levy to sharpen the dialogue. However, the idea for the British Museum finale - which established the Hitchcock tradition of staging set-pieces on famous landmarks - came from Michael Powell (although John Longden had recently starred in Maurice Elvey's 1928 drama, Palais de Danse, which had included a building with a glass dome). The sequence was achieved using the Schüfftan Process - which Hitchcock had probably first seen on his sojourn in Germany and which allowed live action to be combined with paintings and/or models via a mirror placed at 45° to the lens - and it instigated a fascination with technology that would enable the Master of Suspense to keep conducting visual experiments to the end of his career.
Over 75 years on, Blackmail now feels a little creaky. But Hitchcock's intuitive use of sound remains remarkable. Music is employed as source rather than as a novelty and the sequence in which Alice is lacerated by the repeated use of the word `knife' by her gossiping neighbours on the morning after the murder has lost none of its devastating psychological power.