I thought it was much drinking of Lucozade???You're right @staffordjas
It not only involves much drinking of cider, you are meant to venture out at Midnight on the Summer Solstice whilst wearing a wreath of Ivy round your head, all the while chanting to the Moon God. Dancing round a large Oak tree, It is meant to bring on a good harvest for the coming months.
It can also be used as a fertility dance, this is an evening ritual, it involves sacrificing a soul to the man of fire, while paying homage to the Gods of your ancestors. You have to copulate openly in the fields, teach others of the phallic association of the Maypole, and place toads in the mouths of the ill to cure sore throats.
All the while denying the very existence of the human sacrifice. It culminates in the head of the ''man of fire'' collapsing in flames, revealing the setting sun.