"An artist stands before a large sheet of paper on a stage or platform and draws lightning speed sketches of Henry Campbell-Bannerman (Bannerman), Devonshire, Harcourt, Arthur Balfour and Lord Rosebery. 

(Footage is speeded up, but he's still pretty fast!) He then starts to sketch Joseph Chamberlain, starting with the letters 'JOE', and drawing the face around them - very clever. Stop-frame animation makes two arms appear either side of the finished drawing, with a bundle in each, reading 'Protection' and 'Free Trade', respectively."

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Previously:
Lightning Sketch Artists Part 1
Lightning Sketch Artists Part 2
Lightning Sketch Artists Part 3
via British Pathé (Link to YouTube)