same city of York was the scene of another imperial death, the consequences of which were considerably more important to world history. The reigning Emperor at the time was Diocletian, who had soon found his empire too unwieldy, his enemies too widespread and his lines of communication too long to be properly governable by any single monarch. He therefore decided to split the imperial power into four. There would be two Augusti–himself and an old and beloved comrade-in-arms named Maximian–and two rulers with the slightly inferior title of Caesar, who would exercise supreme authority in their allotted territories and would ultimately become Augusti in their turn. The supremacy in northwestern Europe–with special responsibility for the reimposition of Roman rule in rebellious Britain–he entrusted to one of his most successful generals, Constantius Chlorus, who became one of the first two Caesars. The other Caesar was Galerius, a rough, brutal professional soldier from Thrace, who was given charge of the Balkans.
Then, in 305, there occurred an event unparalleled in the history of the Roman Empire: the voluntary abdication of an Emperor. Diocletian decided that he had had enough. He retired to the enormous palace he had built for himself at Salona (the modern Split) on the Dalmatian coast, and forced an intensely unwilling Maximian to abdicate with him. Overnight, Constantius Chlorus found himself the senior Augustus, but he was not to enjoy his inheritance for long. A few months later, on 25 July 306, he died at York, his son Constantine at his bedside. Scarcely had the breath left his body than his friend and ally, the delightfully named King Crocus of the Alemanni, acclaimed young Constantine as Augustus in his father’s stead. The local legions instantly took up the cry, clasped the imperial purple toga round his shoulders, raised him on their shields and cheered him to the echo.
At this time Constantine was in his early thirties. On his father’s side his lineage could scarcely have been more distinguished; his mother, Helena, on the other hand, far from being–as the twelfth-century Geoffrey of Monmouth (and, more recently, Evelyn Waugh) would have us believe–the daughter of Coel, mythical founder of Colchester and the Old King Cole of the nursery rhyme, was almost certainly the offspring of a humble innkeeper in Bithynia. 33 (Other, less reputable historians have gone so far as to suggest that as a girl she had been one of the supplementary amenities of her father’s establishment, regularly available to his clients at a small extra charge.) Only later in her life, when her son had acceded to the supreme power, did she become the most venerated woman in the Empire; in 327, when she was already over seventy, this passionate Christian convert made her celebrated pilgrimage to the Holy Land, there miraculously to unearth the True Cross and thus to gain an honoured place in the calendar of saints.
But let us return to Constantine. The first thing to be said is that no ruler in all history–not Alexander nor Alfred, not Charles nor Catherine, not Frederick nor even Gregory–has ever more fully merited his title of ‘the Great’; for within the short space of some fifteen years he took two decisions, either of which, alone, would have changed the future of the civilised world. The first was to adopt Christianity–the object, only a generation previously, of persecutions under Diocletian more brutal than any that it has suffered before or since–as the official religion of the Roman Empire. The second was to transfer the capital of that empire from Rome to the new city which he was building on the site of the old Greek settlement of Byzantium and which was to be known, for the next sixteen centuries, by his own name: the city of Constantine, Constantinople. Together, these two decisions and their consequences have given him a serious claim to be considered–excepting only Jesus Christ, the Prophet Mohammed