From Thomas Walsh's History of the Irish Hierarchy:
In this territory were many episcopal sees Clonard, Duleek, Kells, Trim, Ardbraccan, Donshaghlin, Slane and Foure. Except Duleek and Kells, they were united before the year 1152 and the common see fixed at Clonard, the sees of Duleek and Kells were also incorporated. In the fifth century the present county of Meath and the greater part of Westmeath were the residences of kings princes and warriors.
In the year 79 of the Christian era the reigning monarch of Ireland, Tuathal, having gained successive victories over the Albanians and his domestic foes summoned a general convocation of his princes and nobles to Tara, the monarch during the session of this national assembly obtained a tract of land from each of the four provinces in each of which he erected a palace and these tracts now form the territory of Meath and Westmeath. The site of the royal residence erected on the Munster tract was called Flactga, that of the Connaught tract was called Visneach, and the third royal seat belonging to Ulster was Tailtean. The palace of Tara was reserved for the monarch himself and here the estates of the kingdom assembled at stated times in order to institute such laws as the well being of the country demanded.
The festival of Easter was approaching and St. Patrick resolved to celebrate this holy festival in the vicinity of Tara where the monarch and his princes were in convocation assembled. The apostle of Ireland determined to proclaim the mysteries of redemption at the seat of government and before the princes of the nation guided by the example of St. Peter who planted the cross in the imperial city of Rome then mistress of the nations and the patroness of error and superstition as she is now the spiritual mistress of Christ's kingdom on earth and the seat of truth and faith refreshing the people of the universe with the waters of her apostolic fountain. St. Patrick and his companions having reached the plain in which the palace of Tara was situated lodged in the house of a respectable man named Sesgnen by whom they were hospitably received. In reward of his kind treatment he obtained the grace of conversion with his family and his son Benignus who accompanied the Saint to Tara, became the companion disciple and successor of the apostle in the see of Armagh.
In compliance with an usage which was sanctioned by venerable antiquity St. Patrick ordered the paschal fire to be enkindled and thus at once attack in its stronghold the national superstition. This primitive custom of lighting the paschal fire was observed in memory of the resurrection of Christ. The ancient Irish worshiped the sun and this luminary was considered by them as the principal and supreme Deity, hence it is that fire worship was the leading dogma of Irish superstition. In compliance with an annual rite the king and princes of the country were celebrating a festival and in conformity with the Druidical worship the eve of that festival was observed with peculiar religious solemnity. By a standing law all the fires of the country were on this eve to be extinguished and no one was permitted under pain of death to kindle a fire until the sacred one should be first lighted on the hill of Tara, as a signal for the rest of Ireland. In violation of this law, the paschal fire was enkindled on the hill of Slane and, when seen from the heights of Tara, the king and his princes became alarmed and enraged at this opposition, as they supposed to the laws and religion of their country.
"This fire which we see, unless extinguished this very night," said the magi to the monarch, "will burn for ever and moreover will excel all the fires of our rite and he who kindles this fire will scatter your kingdom." Leogaire the monarch then enquired who these were who dared to infringe the law and incur the penalty which the national code enjoined. The king in company with two of the magi and attended with a numerous retinue proceeded to the place where St. Patrick had erected a temporary habitation and, having ordered the Saint to be brought before him, St. Patrick obeyed without delay, and before his arrival in the presence of the monarch, it was arranged that no mark of kindness or attention should be paid him, however, when the Saint was ushered into the royal presence. Here the son of Dego, in disregard of this uncourteous ordinance, arose and accosted him with a kindly salutation. The holy man in return imparted his benediction to the noble and generous youth who greeted his approach, nor was it bestowed in vain, as through the Divine goodness the grace of his immediate conversion to the faith was annexed.
Though the national code enjoined the penalty of death on those who violated the law relative to the observance of the national ceremony it does not appear that the monarch or the magi desired its enforcement. On the contrary, the interview with St. Patrick seemed to allay the fears of the king and conciliate his benevolence towards those strangers. On the morning which calls to our minds the glorious event of Christ's resurrection, St. Patrick for the first time proclaimed the Gospel and the mysteries of redemption to the monarch and nobles of the land assembled in the halls of Tara. On this occasion the most eminent of the bardic institute, Dubtach, arose and saluting the Saint became a Christian. In the national assembly, the bards of Ireland were particularly revered. Theirs were the duties of recording in harmonious strains the achievements of their countrymen, the wisdom of the senator, the bravery of the chieftain, the exploits of the patriot. The care of preserving an exact registry of the genealogies of families and the prerogatives of the nobles and of the boundaries which marked out the possessions of the chieftains was confided to the members of this order and it was wisely ordained that at stated times their writings should be submitted to a tribunal over which the monarch himself and a certain number of nobles presided. Before this tribunal the works of the bards were examined and from the entire collection extracts duly authenticated were deposited in the royal archives of Tara. The acquisition of Dubtach to the cause of truth was a just tribute to the force and power of the Saint's address and which was as irresistible as that of St Paul to the Areopagus at Athens. By it was torn up the bias of education and the prejudice of habit and others followed the powerful example which the conversion of the chief bard afforded in his own person. Yet the monarch hearkened not to the voice of truth but remained obstinate in his superstition although he granted permission to St. Patrick to preach the Gospel on condition that the peace of the kingdom should not be disturbed. St. Patrick, on the following day, repaired to Tailtean, where public amusements were celebrated and which were attended by the court of Tara. There also he multiplied the number of his converts and among them was Conall, brother to the king, who believed and was baptized. Visiting other parts of Meath his preaching was everywhere attended with success. Having erected a church at Drumconrath in the barony of Slane and one at Dromshallon near Drogheda, he directed his course to Delvin and thence to the hill of Usneagh, reducing the whole mass of the people to the sweet yoke of the Gospel.