The kingdom came to an end at the dawn of the 17th century after Conn O'Neill, the last head of the Clandeboye O'Neills of Upper Clandeboye, signed away two-thirds of his land to his close associates Hugh Montgomery and James Hamilton who proceeded to privately settle their land with settlers from Great Britain just prior to the larger Plantation of Ulster.

They were Gallowglass soldiers under the leadership of the MacDonnell of Antrim who had established themselves by the mid-16th century as Lords of the Glens (the remaining parts of the area which Normans had previously held as the Earldom of Ulster).

During the 1550s and 1560s, Shane (later known as "the Proud") arose to assert his rights, protesting to Elizabeth I and inflicted notable military defeats on establishment figures such as the Earl of Essex.

[6] Brian McPhelim and some of his relatives acted as intelligence agents to Piers, playing a role in undermining Shane at the Battle of Farsetmore in 1567.

Seeing himself as in a secure position, Brian McPhelim decided to flex his power and waged a private war against the Tyrone successor of Shane, Turlough Lynagh O'Neill.

[6] A year after the death of his father, Turlough had declared loyalty to Elizabeth I and so Brian McPhelim's adventurism did not impress the authorities.

Essex, who had only recently been made an Earl, encouraged by Lord Burghley, was more directly involved on the ground and had most of his fortune at stake.

Haunted by an outbreak of plague at Carrickfergus in 1573–74, which decimated Essex's forces, he fled to the English Pale, being based at Dublin and Drogheda for the rest of his time, only entering Ulster on raids against O'Neill and others.

[6] Sir Brian McPhelim, his wife and his half-brother Rory Oge MacQuillin were all taken hostage to Dublin where they were hanged for opposing the plantations.

This conflict, in alliance with Habsburg Spain, was a predominantly Ulster-based Irish Rising against Protestant English rule and brought together what were usually enemies such as the O'Neills of Tyrone and the O'Donnells of Tyrconnell in common cause.

Only minor engagements, no major battles, took place as the area had suffered significant depopulation due to the conflicts brought about by Essex and Smith's attempted colonisation.

[6] The main negative effect on Clandeboye was the actions of Arthur Chichester after 1601, who set about burning destroying crops and animals as well as killing men, women and children without scruple.

Historical records of the period say that in Clandeboye as a result of Chichester's acts, the people were reduced to cannibalism, corpses had green-mouths from eating grass and dead bodies were piled by the roadsides.

[6] This destruction was supposedly to stop Clandeboye being used as a supply base for Tyrone, but had a secondary purpose as, Chichester, in financial difficulties from his estates Devon, sought land to take in Ireland.

[6] Conn McNeill O'Neill, the Lord of Upper Clandeboye, who was based at Castlereagh, was arrested around Christmas of 1602 (a year after his father Niall McBrian had been killed by Captain Malby).

Fortune favoured Conn McNeill as, on the death of Elizabeth I, James VI of Scotland ascended to the thrones of England and Ireland in July 1603, with the opportunity of a clean slate.

Famously, Captain Conn O'Neill of the French Army was present at the Battle of Culloden in 1746 and was instrumental in asking Flora MacDonald to help Bonnie Prince Charlie escape the Redcoats from the island of Benbecula in the Outer Hebrides.

They served the Royalist cause during the Wars of the Three Kingdoms and after showing bravery at the Battle of Edgehill, Niall Oge's son Sir Brian O'Neill was awarded with the Baronetcy of Upper Claneboys.

After being nudged out of power by junior lines who divided Clandeboye, the senior branch of the family (who retained property in Toome for a time), were implicated in Tyrone's Rebellion, served under Owen Roe O'Neill in his Ulster Army of the Irish Confederate Forces (in the form of Colonel Ever O'Neill) and then Felix O'Neill (died 11 September 1709), his son, served as part of Lord Galmoye Regiment in the Jacobite Irish Army, before prolifically serving in the Irish Brigade of the Royal French Army.

In 1896, this Jorge submitted his genealogy to the Somerset Herald in London: he was subsequently recognised as having the only pedigree in the Office of Arms showing descent from the "Princes of Tyrone and Claneboy."

Others such as Edmund Spenser (for whom Gaelic society was a remnant of "Scythian barbarism") were intellectually connected to this circle but not overtly in the Enterprise, more involved in the Munster Plantation.

These men were influenced by the classics and in particular Livy and Cato the Elder's axiom Carthago delenda est (in their ideal, Gaels were analogous to Carthaginians).

He imagined a completely demilitarised Ulster, where no Gael (Irishman or Scots), whether kerne or Gallowglass, would be allowed to bear arms, even spear or axe, on pain of capital punishment.

The Irish Gaels of Clandeboye were to be "dispersed into severall Lordshippes and well corrected, yf they breake lawes", those who remained in the area would be reduced to disarmed helots, tiling the land in agricultural labour under English overlordship.

The contemporary John Derricke's The Image of Irelande, with a Discoverie of Woodkarne (dedicated to Philip Sidney) further dehumanised the Irish kerns as "noisome worms" and called for Gaels to be "extirped and abolished clean the land."

An English official in Belfast during the Clandeboye campaign, Edward Berkeley urged using famine as a weapon of war against the locals, bragging that grain had been taken from them so they had to rely only on milk (which was "easily taken away"), commenting on their starvation he said; "How godly a dede it is to overthrowe so wicked a race the world may judge.

The most controversial act of Essex's tenure in Clandeboye was the Clandeboye massacre in November 1574, whereby, at a feast in Belfast Castle, hosted by Sir Brian McPhelim O'Neill who was attempting to make peace, Essex ordered his men to indiscrimanently and without warning massacre 200 men, women and children associated with his host.

Other prominent monasteries include the Norman-founded establishments of Grey Abbey, under the Cistercians and Newtownards Priory, under the Order of Preachers (Dominicans).

The local chapel of importance to the O'Neills was Knockollumkille, near their headquarters at Castlereagh, founded by Columba of Iona in much earlier times.

By the start of the 18th century, it was no longer in use and all that remains of the actual building of this Church today is part of a wall of the Knock Burial Ground, Clarawood, Belfast.