In 1924 the poet André Breton published the Surrealist Manifesto in Paris. The key figure behind it was the Austrian psychologist Freud — who, a few years earlier, had convinced all of Europe: you think you control yourself, but in fact your unconscious controls you.

The Surrealists turned this idea into a creative method: ‘automatic writing’ to let the unconscious pour straight out; the ‘exquisite corpse’, several people drawing one picture together; and most famous of all — Salvador Dalí, using his ‘paranoiac-critical method’ to paint dreams as precisely as photographs.

Melting clocks, a pipe captioned ‘Ceci n’est pas une pipe,’ clouds with a woman’s face — these images may look like memes today, but in the 1930s they genuinely unsettled people. Surrealism later became advertising’s best weapon: every visual gag that makes you go ‘huh?’ and then ‘ah!’ traces its source back here.