In England, the movement came out of Left Wing politics and poetry as well.
The first big happening was a poetry reading staged at Albert Hall. Booked on a whim, they were surprised to see it sell out. It was filmed by Peter Whitehead as “Wholly Communion” (1965) (he later made Let’s All Make Love In London in 1967 with The Pink Floyd and others).
Both are in full length (1 hour+ each) on youtube.