In 1216 King Henry III. granted the manor of Swords with increased privileges to Henry de Loundres, Archbishop of Dublin, on condition that he should build and maintain a castle on his manor of Castle Kevin. Nearly two centuries later, Swords was seized by the Commissioner of Forfeitures on the plea that this had not been done, but it was afterwards returned to the Archbishop of the time as having been unjustly taken.

The fortress was intended for protection in this direction against the invasions of the O’Byrnes and O’Tooles. The site was some three and a half miles north-east of Glendalough, the ancient cathedral city of that diocese. Its natural defences were the bog, on the edge of which it stood, and thick woods that stretched almost from Dublin to Glendalough. Quite close to it ran a stream, which joined the Avonmore about a quarter of a mile lower down, near the present village of Annamoe.

It appears to have been a square building, flanked by towers at each corner. The foundations, which still remain, measure some 120 feet each way. They are elevated about 20 feet, and are now covered with grass.

The castle was built of rubble stone and excellent mortar, which is shown by the huge blocks of the walls which still lie round the foundations.

The Archbishops held courts and exercised jurisdiction here through their officers, and had their own gallows.

In 1277-78 the Treasurer’s account for the year contains £60 to John de Saunford for the custody of the new castle of Mackinegan and Castle Keyvin. The stronghold was often used by the Archbishops as a hunting-lodge, the woods around being well stocked with deer. It was also strongly garrisoned.

At the beginning of the next century (1308) the Viceroy Wogan marched against the O’Tooles, but was defeated with the loss of several knights. Castle Kevin was captured and the garrison killed, while the towns near were sacked and plundered.

Later Piers de Gaveston successfully subdued the rising, and made a thanksgiving offering at the Church of St. Kevin, Glendalough. The following year he built New Castle in the O’Byrnes’ country and repaired Castle Kevin, at the same time cutting a pass through the woods, from it to Glendalough.

Thirty years later Alexander de Bickner received royal orders to repair his fortifications at Castle Kevin, so that at this time it was still connected with the See of Dublin, but it subsequently passed into royal keeping.

It appears that Henry VIII. by letters patent “made grants to Arte O’Toole and heirs the manor of Castle Kevin and the Farrtree” (hence Vartry) “on conditions they used the English habit, language, education, hostings, aidings, and the like, and that he should keep Castle Kevin in repair as a bulwark against the rebels.”

Phelim O’Toole was the representative of the family in 1591 when Hugh Roe O’Donnell escaped from one of the gate towers of Dublin Castle, where he had been confined as a hostage for over three years.

O’Toole having visited him in prison, as a friend, during this time, he naturally thought he was safe in seeking shelter at Castle Kevin.

Phelim’s loyalty was not, however, above suspicion, and he was divided between his wish to help the young fugitive and fear for his own head. In this difficulty a woman’s wit apparently solved the problem. His sister Rose, wife to the great O’Byrne of Ballinacor, was at Castle Kevin at the time, and she advised him to send a slow messenger to Dublin advising the Lord Deputy of O’Donnell’s arrival, and a fast messenger to her husband in Glenmalure (who was in a state of open rebellion), telling him to come and carry off Hugh before the Government officials arrived.

Phelim followed the advice given, but the “wine-dark” Avonmore becoming flooded the party of rescuers, at once despatched by O’Byrne, could not cross the river, and the King’s men arrived first upon the scene. Whereupon Hugh O’Donnell was escorted back to Dublin, and was confined in the Wardrobe Tower in irons, from which, however, he escaped the following year.

Captain Charles Montague, writing to the Lord Deputy in 1596, states that Feagh M’Hugh O’Byrne had threatened to besiege the castle with three hundred men, and that he had provisioned it for a month. The same year a ward was placed in it during the rebellion, while in 1599 a commander was appointed to the forts of Rathdrome, Castlekeavyn, and Wicklowe, at ten shillings a day.

No doubt the O’Tooles were implicated in the rebellion referred to, for in 1609 we find John Wakeman, who had received the confiscated estate of the O’Tooles, selling Castle Kevin back to Luke (or Feogh) O’Toole. In the deed recording the transaction it is remarked that the castle for some years past “hath been waste and in utter decay.”

An inquisition of 1636 found that the son of Arte O’Toole, to whom the lands were first granted, had gone into rebellion and died, and that his son Feogh O’Toole who represented the family at the time of the inquiry, had bought back Castle Kevin from the man to whom it had been granted after the confiscation of the O’Toole property. Castle Kevin had at this time been uncovered for thirty years, and this was deemed sufficient for forfeiture, as it had been granted on condition that it should be kept in repair.

Accordingly in July of the same year an ordinance was issued by the King taking possession. The castle and lands were then granted to Sir John Coke, Knight, Secretary of State. Dr. Alane Cooke, writing to him from Dublin in August describing his new property, says:—“Castle Kevin, the town where the castle doth stand; this hath a goodly wood, but no great timber and very fine young oaks;” and again:—“Castle Kevin is the fittest place to build the manor, because of the strength. The bawn is very good, very near 20 feet high. All the castle is down and the bounds are very nearly 50 yards square, a fine small river running at the foot of the castle.”

The grant of land consisted of 15,441 acres of all sorts, English measure, 12 miles from Dublin, with a castle called Kevin, and a fine river full of salmon and trout.

It does not appear, however, that Luke O’Toole was easily dislodged, and when Oliver Cromwell left Dublin to march to Wexford in 1649 he proved a source of constant annoyance to the troops. At this time he was encamped at Glenmalure with his four sons, one of whom managed to seize Cromwell’s favourite steed. Its owner offered £100 to Luke for its return, “but for gold or silver he would not give him back, but preferred to keep him as a monument.”

It is said that in revenge for this Cromwell ordered his cannon to level Castle Kevin. Local tradition supports this statement by pointing out a furze-covered rath from which the castle is supposed to have been shelled by Ludlow, while the blocks of adhering masonry round the foundations are unlike the crumbling of age alone.

Against this it is remarked that Castle Kevin does not appear in the list of Leinster castles reduced by Cromwell. This, however, might be accounted for from the fact that (as it appears) only a part of the castle walls were standing at the time, and that its final destruction had no strategical value, but was merely private revenge for the theft of a horse, and so was not recorded.

Luke O’Toole was afterwards captured and executed.

The land upon which the remains of the castle stand is now in the possession of the Rev. Charles Frizell, who also owns the modern manor house of Castle Kevin, some quarter of a mile distant, on a hill above the ancient building.