Note 148 — BOOK I.
Reading edition
The poet here introduces a distinction, well known in heraldry. The banner was a square flag, which only barons of a great lineage and power had a right to display. The pennon was a forked streamer borne by a knight: Theseus carried both to the field, each bearing a separate device. Chaucer says,
"And by his banner borne is his pennon."