What is a butt tuba and why is it in medieval art?

A rabbit attempts to play a church organ, while a knight fights a giant snail and a naked man blows a trumpet with his rear end. These bizarre images, painted with squirrel-hair brushes on vellum or parchment by monks, nuns and urban craftspeople, populate the margins of the most prized books from the Middle Ages. Michelle Brown explores the rich history and tradition of illuminated manuscripts. [Directed by WOW-HOW Studio, narrated by Adrian Dannatt, music by Jarrett Farkas].