Clennell was one of the Ten Towns of Coquetdale which owed service to Harbottle Castle. It was first mentioned in the grants to the monks of Newminster by the Umfravilles, who were the Barons of the area after the Norman Conquest.
The boundary or march was mentioned in the charter of Odin de Umfraville, the builder of Harbottle Castle, in 1181. It was again mentioned and described in detail by Richard de Umfraville around the year 1200 as being:
‘From a cross which the monks caused to be placed for a boundary at Allerhopeburn Head going down by Allerhope burn to the Alwin towards the south, then to the place where Kidland burn flows into the Alwin, and so to the west up Kidland burn to the ditch which the monks made as a boundary between their land and the land of Thomas of Clennell and so by the ditch to Redepath on the great road that leads to Yarnspath and so by that road to the stream of Yarnspath’
The Abbot and monks made a treaty with Thomas of Clennell to allow them to travel through his land with their sheep and cattle. In return they promised that he would be buried in the Abbey as a monk and that prayers would be said for his soul, plus he would get a pair of boots every year.
Thomas of Clennell did homage to Edward I at Berwick, but from 1303 to 1308, he was kept a prisoner in the Castle of St. Brexel on the banks of the Wye, probably for having taken the side of the Scots against Edward I, for, like many of the border chieftains, the Clennells were sometimes in the service of the Scottish King and at others on the side of the English.
William Clennell, Esq. was constable of Harbottle Castle in 1434, and in 1541 Persival Clennalle was one of the Gentlemen Inhabitants within the Middle Marches and owner of Clennell tower. The Border Survey of 1541, says :
“At Clennell ys a lytle toure of the inherytaunce of one P'cyvall
Clennell, gent, newly reparelled and brattyshed by the same
Percivall. And also he ys in makinge of a newe barmekyn
about the same as his power will extende thereunto."
Clennell tower is not included in the 1415 list of border fortresses, neither is it mentioned in that of 1509. Slight traces of what appears to be a date are visible on the door head, which has been variously read 1313 and 1365, but seeing that 1541 is the first notice there is of the tower, it was most likely built between the years 1509 and 1541. The tower measures 22 feet from east to west, 30 feet from north to south, and has walls 6 feet thick. The stone arched basement, now used as a cellar, is divided by a modern partition, but still retains its original features, and has a fine deeply splayed loop untouched by the restorer. Over a window in the old drawing room on the first floor of the tower, is seen a piece of a frieze carved in bas relief (of an unknown date) representing a scene after the style of Chevy Chase, pronounced by the noted Northumbrian historian Cadwallader Bates to be " The most interesting bit of ancient work he had ever seen in Northumberland."
Percevall Clennell, of Clennell, was with Lord Francis Russell when he was killed by the Scots on the heights of Windy Gyle in 1585. The names of the freeholders in Clennell in 1568 were Nicholas Forster, John Wilkinson, and Richard Pratt. In the list of freeholders of "Cokedale Ward 1628" the name of Robert Clennell, of Clennell occurs, while that of George Clennell of Clennell, Gent. is given in a similar list for Cockdale Warde in 1618.
The Rates and Rentals for 1662 records Mr. Thomas Clennell as the proprietor of Clennell, the rental £90 and also part of Newton, for the Tyth of £15
In the lists of papists and non jurors presented at the Quarter Sessions of April 29, 1685, the name of Thomas Clennell de Clennell, the said Thomas being bound in the sum of twenty pounds to appear at the Sessions when required by proclamation.
Luke Clennell of Clennell, Esq., was Sheriff of the County in 1727. The names of Luke Clennell's family are recorded in the Register of Baptisms at Alwinton. His eldest son, Thomas Clennell, left a daughter, who married William Wilkinson, who thus came into the possession of Clennell. He was High Sheriff of Northumberland in 1758. Percival, the youngest son, born in 1714, was the first of the names who took up his residence at the new Harbottle Castle, that part of the estate having been left to him by his niece. The Alwinton Burial Register contains the following entry:
1796, March 16. Percival Clennell, Esq., HarbottIe."
The next proprietor was Mr. Anthony Wilkinson, of Prince's Gardens, London and the great -grandson of the first of the name at Clennell, who made extensive additions to the mansion in which he incorporated the original structure and introduced the electric light and other modern improvements, thus transforming the old border tower of the Clennells into a country residence.