Bicycle window

After several attempts I finally got to see the famous bicycle window in St Giles church, Stoke Poges this afternoon.

The stained glass dates from 1643, and the image appears to show a naked cyclist on a "hobby horse" blowing a trumpet.

As....

a) the "hobby horse" was not invented until the nineteenth century
b) The Naked Bike Ride idea didn't emerge until 2004

...there is presumably some other explanation for what is going on here.