type of all is the British warship; for now Britannia, for the first time, ruled the waves, and was, indeed, so entirely Mistress of the Sea that her fleet appeared even in Mediterranean waters.[322] The vessels figured are invariably not Saxon “keels,” but classical galleys, with their rams and outboard rowing galleries, and are always represented as cleared for action (when the great mainsail and its yard were left on shore).

A. 5.—­The usurpation of Carausius, “the pirate,” as the Imperial panegyrists called him,[323] brought Diocletian’s great reform of the Roman administration within the scope of practical politics in Britain.  The old system of Provinces, some Imperial, some Senatorial, with each Pro-praetor or Pro-consul responsible only and immediately to the central government at Rome, had obviously become outgrown.  And the Provinces themselves were much too large.  Diocletian accordingly began by dividing the Empire into four “Prefectures,” two in the east and two in the west.  Each pair was to be under one of the co-Augusti, who again was to entrust one of his Prefectures to the “Caesar"[324] or heir-apparent of his choice.  Thus Diocletian held the East, while Galerius, his “Caesar,” took the Prefecture of Illyricum.  His colleague Maximian, as Augustus of the West, ruled in Italy; and the remaining Prefecture, that of “the Gauls,” fell to the Western Caesar, Constantius Chlorus.  Each Prefecture, again, was divided into “Dioceses” (that of Constantius containing those of Britain, Gaul, Spain, and Mauretania), each under a “Vicar,” and comprising a certain number of “Provinces” (that of Britain having four).  Thus a regular hierarchy with rank above rank of responsibility was established, and so firmly that Diocletian’s system lasted (so far as provincial government was concerned) till the very latest days of the Roman dominion.

A. 6.—­When Constantius thus became Caesar of the West, his first task was to restore Britain to the Imperial system.  He was already, it seems, connected with the island, and had married a British lady named Helen.[325] Their son Constantine, a youth of special promise (according to the panegyrists), had been born at York, about A.D. 274, and now appeared on the scene to aid his father’s operations with supernatural speed, “quasi divino quodam curriculo."[326] Extraordinary celerity, indeed, marked all these operations.  Allectus was on his guard, with one squadron at Boulogne to sweep the coast of Gaul, and another cruising in the Channel.  By a sudden dash Constantius [in A.D. 296] seized the mouth of Boulogne harbour, threw a boom across it, “defixis in aditu trabibus,” and effectually barred the pirates from access to the sea.[327] Meanwhile the fleet which he had been building simultaneously in various Gallic ports was able to rendezvous undisturbed at Havre.