He was the inventor of ‘art brut’ who rebelled against his parents, his teachers and then art itself. Yet the impact of his wild provocative paintings, often culled from graffiti, can still be seen today

Which great artist of the 20th century has been most influential on the 21st? Neither Picasso nor Matisse, as they have no heirs. And not Marcel Duchamp, however much we genuflect before his urinal. No, the artist of the last century whose ideas are everywhere today was a wine merchant who took street art and fashioned it into something extraordinary more than 75 years ago.

After four years of Nazi occupation, you’d think Parisians would have been unshockable. But in 1944, the newly liberated city was sorely provoked by the antics of Jean Dubuffet. Even as the last shots were fired, he was creating newspaper collages bearing the fragmentary graffiti messages he saw in the streets: “Emile is gone again”, “Always devoted to your orders”, “URGENT”. In the next couple of years, he unveiled shapeless, childlike paintings that abandoned all pretence at skill.