Padstow is a Cornish fishing village on the northern coast, where they celebrate Mayday with an all-day festival that includes a hobby horse, locally called the 'Obby Oss'.
It actually starts the night before, when the pubs close and the people start the night singing. It's a bit like Christmas carolers, visiting homes and singing to the occupants.

In the morning, the children start out first - with a small version of the Oss. The scouts used to have one and other children, over the years, have made their own. They dance this 'beast' all around the streets, with a band of dancers and musicians - drummers and accordian/melodian players. Most of the followers are dressed in white, with either blue or red ribbons and matching bandanas, and one dancer, carrying a thing that looks like a padded table-tennis bat, is the teaser. He or she dances in front of the Oss, teasing and leading him on. The children finish before the big adult Osses appear.

The Oss looks like a circular table with a big black table cloth. There is a hole in the middle for the person carrying it to put their head through and he has a pointed mask, almost like a witches hat, covering his face. The 'table' has a pole with a stylised head sticking out one side and a 'tail' stuck out the other side. The whole thing looks almost African, painted black with red and white markings - eyes, nose, ears and mouth.
Then at 10am the Blue Ribbon Oss leaves its 'stable' and, with the streets full of people, they begin their dance. The Red Ribbon Oss starts one hour later and they each have their own route, avoiding the others until a specified time when they 'meet' under the maypole and have a mock battle. During the day the Oss will chase the girls and they do say that "if you get caught under the Oss, you'll be married before the end of the year" (or you will have to get married because...) (This is a fertility festival, after all.)
This continues throughout the day, with only short meal breaks, until late at night, when the Oss is put back in his stable for another year, amid tears from the revellers.
This festivity has several magical aspects:
If the Oss is a strong dancer and catches lots of girls, the farmers will have lots of baby horses and sheep and sons - all necessary for a small-farmer to survive in past centuries.
As the Oss dances past the harbour, he is taken to dip his face in the water and he splashes his followers. This is also sympathetic magic - a rain charm this time.
At regular intervals during the song (the same one that they sing all day) the Oss 'dies' and the crowd sing a special dirge. At the end, they yell out "OSS OSS" and others reply "WEE OSS", the Oss comes back to life and the dancing starts all over again. This is said to be a pre-christian example of death and resurrection, and is to encourage the plants that 'died' in the winter, to come back to life in summer.
People do say that if the Oss didn't dance, the summer wouldn't come and while they don't really believe that any more, just in case, they wouldn't give it up. Besides, it's a great excuse for a major booze-up! And these days, when tourism has become the life blood of Padstow, this certainly brings in thousands of people, all buying pasties for lunch and drinking lots of beer.

Steeleye Span have a civilised version of the Oss song on their CD 'Tempted and tried' (only I don't know how to do a blicky to it) but the street version is much more primitive.
The occasion has attracted several 'folk' over the years - Hamish Henderson would always turn up and the Spinners from Liverpool. Also, the Watersons and Martin Carthy have been known to go to Padstow for Mayday too.
And I've been twice - and joined the Blue Oss band both times! I've been accepted by the locals as a 'local'! How's that for genealogy meets folk??
OSS OSS!
Robyn