The death of Constantius occurred soon afterwards in England, at the city of York (Eboracum), and there he was succeeded as Emperor of Rome by his son Constantine.
Constantius had in some degree restrained the persecution of the Christians in Britain, which had raged under Diocletian, but it was now completely suppressed by the new emperor. Carrying with him his faith in Christianity, which he had learned in Britain, Constantine removed to the continent to engage in the contest for the command of the empire to which he had fallen heir, and in the battle of the Milvian Bridge, near Rome, in A.D. 312, he defeated the opposing eastern forces under Maxentius, and entered into undisputed possession of his position as sole emperor. It was just before this engagement that Constantine is reported to have seen a cross shining in the heavens at midday, having on it the inscription, ΕΝ ΤΟΥΤΩ ΝΙΚΑ ("In this conquer"—"In hoc signo vinces"), and, therefore, recognizing the Christian emblem, he adopted the Christian cross as his standard and placed the sacred monogram upon his Labarum. This victory resulted in the official recognition of the Christian religion, and the attaching to it of all the political power of the Emperor of Rome.
Constantius had lived, and Constantine the Great had been born and brought up, in the north of England, which, during the Roman occupation, had been converted to Christianity by missionaries from Scotland, whence St. Patrick afterwards also went to Ireland; and as it was to Constantine that the Christians owed their rescue from persecution, his insignia would, therefore, be heartily received. The early Christians, through this source, may have adopted the X cross, the lower part of Constantino's Christian monogram, as their emblem, and thus it had become associated in Ireland with the Christian labours of St. Patrick, their apostle and patron saint. In this "story of the Irish Jack," it is a notable transition that the harp emblem of Hibernia, carried by Constantius, and transmitted by him to his son, and by Constantine changed to the Christian Labarum, should in this diagonal cross of St. Patrick have been returned to become the emblem of Ireland.
Whichever may have been the source of its origin, the saltire cross, in its form of the red cross of St. Patrick, is by both lines of descent intimately associated with the history of Ireland, and is rightfully claimed as one of its national emblems.
The harp, too, has its story much later than that of St. Patrick's cross, but yet bringing an interesting connection with the patron saint.
The ancient arms of Ireland, from the time of Henry II., in 1172, had been three golden crowns set upon a blue ground.[76]
These ancient arms of Ireland are the arms of the Province of Munster, and are now worn on the helmet plate and glengarry of the Royal Munster Fusiliers regiment of the British army.
Henry VIII. was the first English king who used an Irish emblem. When he was proclaimed King of Ireland, he placed the harp of Hibernia upon the coinage which he then issued, instead of the "three crowns" which had been used under his predecessors, but he did not introduce the harp into his royal arms, nor place the red cross of St. Patrick upon his banner.
The first English monarch to insert an Irish emblem in the official insignia of the sovereign was Queen Elizabeth, who introduced one in the design of her "Great Seal." Instead of using the three Irish crowns, she inserted a harp as the emblem of the Irish nation, and among the banners displayed at her funeral Ireland was represented by a blue flag having upon it a golden harp surmounted by a crown.[77] James I., her successor, was the first king to introduce an Irish emblem into the "royal standard," and from that time onward the golden harp of Hibernia, on the ancient blue ground of the three Irish crowns, has been shown in one of the quarters of the British standard as the emblem of Ireland. In the arms of all the sovereigns, from James I., 1603 (15), to and including William IV., 1837, the front of the harp was formed by the female figure representing the goddess Hibernia. During the Victorian period a change was introduced in the shape of the harp, which has been altered to that of the ancient Irish harp, connected in form and legend with King Brian Boru (Boroimhe).
The exploits of this most noted of the early kings of Ireland had been mainly devoted to the defence of his kingdom against the invasions of the Danes during the period when, under Canute, they had well-nigh conquered all England.