Which self-taught freethinker broke from British literary form and content traditions to write poetry in this characteristic style?

The self-taught freethinker who broke from British literary traditions to write poetry in a unique style was Walt Whitman. Whitman's poetry in "Leaves of Grass" was revolutionary in both its form, with its free verse and unconventional structures, and its content, which celebrated the individual, nature, and democracy. His work marked a significant departure from the traditional British poetry of his time.