So also Procopius, lib.1.Vandal. speaking of the same Constantine,saith: Constantine being overcome in battle, was slain with his children. Yet the Romans could not recover Britain any more, but from that time it remained under Tyrants. And Beda, l.1.c.11. Fracta est Roma a Gothis anno 1164, suae conditionis; ex quo tempore Romani in Britannia regnare cessaverunt. And Ethelwaldus: A tempore Romae a Gothis expugnatae, cessavit imperium Romanorum a Britannia insula, & ab aliis, quas sub jugo servitutis tenebant, multis terris. And Theodoret, serm. 9.
de curand. Graec. affect. about the year 424, reckons the Britons among the nations which were not then in subjection to the Roman Empire. Thus Sigonius: ad annum 411, Imperium Romanorum post excessum Constantini in Britannia nullum fuit.
Between the death of Constantine and the reign of Vortigern was an interregnum of about 14 years, in which the Britons had wars with the Picts and Scots, and twice obtained the assistance of a Roman Legion, who drove out the enemy, but told them positively at their departure that they would come no more. Of Vortigern’s beginning to reign there is this record in an old Chronicle in Nennius, quoted by Camden and others: Guortigernus tenuit imperium in Britannia, Theodosio & Valentiniano Coss. [viz. A.C. 425.] & in quarto anno regni sui Saxones ad Britanniam venerunt, Felice & Tauro Coss. [viz. A.C. 428.] This coming of the Saxons, Sigibert refers to the 4th year of Valentinian, which falls in with the year 428 assigned by this Chronicle: and two years after, the Saxons together with the Picts were beaten by the Britons. Afterwards in the reign of Martian the Emperor, that is, between the years 450 and 456, the Saxons under Hengist were called in by the Britons, but six years after revolted from them, made war upon them with various success, and by degrees succeeded them. Yet the Britons continued a flourishing kingdom till the reign of Careticus; and the war between the two nations continued till the pontificate of Sergius A.C. 688.