The nunnery was said by a charter to have been founded by William Rufus on 6 January 1089 for black nuns of the Order of St. Benedict in the honour of Jesus Christ and the Blessed Virgin Mary.
It was also claimed that Rufus had granted to the nuns, within their nunnery and lands adjoining, all the liberties which he had conceded to the monastery of Westminster without molestation of any of the king's sheriffs, escheators, bailiffs or lieges.
A claim to the liberty of sanctuary was also made, which was probably related to a square pillar, inscribed with a cross and the words 'Sanctuarium 1088,' which was placed on rising ground above the nunnery.
[2] The reason for the forgery appears to have been to regain losses following devastating raids from the Scots, as recorded in letters patent of Edward IV, 1473.
It seems likely this was the only way to ensure the nunnery's survival, but in doing so the compilation was subject to the unreliability of memory and oral tradition, and was not historically accurate.
The difficulties of surviving in an area so close to the raiders of the borders is shown in the terrible problems recorded in 1473, earlier in 1318 they were not taxed as they were totally destroyed by the Scots.
The property of the nunnery at the time of the dissolution was scattered in Ainstable, Kirkoswald, Cumwhitton, Blencarn, Kirkland, Glassonby, Crofton and Carlisle.