Lesser Britain (as opposed to Great Britain), or Little Britain, still exists today. In Roman times it was part of the territory called Armorican Gaul. Armorica was colonized in part from Britain, perhaps by Britons fleeing the Saxon incursions, c.450. There is a strong linguistic connection between the Celtic language of Brittany and the Celtic languages of Wales and Cornwall, supporting this and possibly even earlier colonization efforts.

            In the Arthurian era, Brittany had a strong connection to Britain, and has all along been an important link in the Arthurian legend. In fact, it is theorized that many of the Arthurian traditions used by Geoffrey of Monmouth were orally preserved there and transmitted to him by the Norman conquerers.

            Geoffrey of Monmouth tells us that the kingdom of Brittany was founded when the Roman emperor/British King Maximianus (meaning Maximus, a Roman who was proclaimed Emperor by the Roman troops of Britain in 383, marched on Rome in 383 and was overthrown and executed soon thereafter) bestowed the land on Conanus Meridiadocus (nephew to Octavius, "King of Britain").

"He [Maximianus] summoned Conanus to him... and said to him with a quiet smile: "Well, we have seized one of the fairest kingdoms of Gaul... You must not let it depress you that you have permitted the kingship of the island of Britain to pass into my hands, when you had hopes of possessing it yourself. Whatever you have lost in Britain I will make good to you in this country. I will raise you to the kingship of this realm. This will be a second Britain, and once we have killed off the natives we will people it with our own race..."
                                                            --Geoffrey of Monmouth, The History of the Kings of Britain (translated by Lewis Thorpe)

            Conanus (Conan, Cynan) was succeeded by Aldroenus, whose brother was Constantine. Constantine returned later to Britain to rule there, and in legend is Arthur's grandfather. The ruler of Brittany was a certain King Hoel in the legends, who reigned according to tradition from 510-545 CE.