Glastonbury Festival 1978
This became known as the “impromptu” Festival.
This happened with the arrival of travellers washed out from Stonehenge who were led to believe that a festival was taking place. After persuasive discussion, a free mini Festival did take place. There was little organisation and few facilities layed on but somehow it did not matter - the stage was powered by an electric meter in a caravan with the cable running to the stage.