The Book of Kells page 291v has a portrait of St John the Evangelist and several square crosses. For this man also named John I drew out of one of those crosses, and then morphed it into more of a high cross shape, to fit an oval to cover the upper part of this body builder's ham of an arm. It helps to have a big canvas when you want a lot of detail in the Celtic knots!
St John Shield tattoo by Pat Fish