This was all very well: Columbanus's success indicates the appeal of his mission. But his activities, for the first time, brought the nature of Celtic monasticism firmly to the attention of the Church authorities -- to western bishops in general, and to the Bishop of Rome in particular. The Irish monks were not heretical. But they were plainly unorthodox. They did not look right, to begin with. They had the wrong tonsure. Rome, as was natural, had 'the tonsure of St Peter', that is, a shaven crown. Easterners had the tonsure of St Paul, totally shaven; and if they wished to take up an appointment in the West they had to wait until their rim grew before being invested. But the Celts looked like nothing on earth: they had their hair long at the back and, on the shaven front part, a half-circle of hair from one ear to the other, leaving a band across the forehead.
Paul  Johnson, A History of Christianity
christianity, hair