"celebrate the solstice with dancing"

Midsummer's Eve has been celebrated in Britain since the 13th century in much the same way as described here: fire, drinking, dancing and sex.  Although it coincides with the Christian celebration of St John the Baptist, the sacred aspect of the festivities frequently lost out to the profane.  A monk in the 15th century records that

"At first, men and women came to church with candles and other lights and prayed all night long. In the process of time, however, men left such devotion and used songs and dances and fell into lechery and gluttony turning the good, holy devotion into sin."