Malcolm II had become king of Scotland the year before. Scottish kings traditionally led a raid early in their reigns to demonstrate military might, and the timing favoured Malcolm: Aethelred II of England was preoccupied fighting Vikings in the south. The lordship of Cumbria had been gifted to Scotland in 973 in exchange for defending the English borders, but Malcolm seems to have wanted the land outright rather than as a fief that required homage. A march south through Northumbria would settle both questions at once - whether English authority extended this far north, and whether the young king of Scots could break it. Durham, with its sacred relics and unfinished defences, made an obvious target. Aethelred's earl in the area was old, the earl of York was indifferent, and the new town on the Wear looked vulnerable.

What Malcolm had not counted on was Uhtred. The son of Waltheof, Earl of Bamburgh, Uhtred was a young man - De obsessione calls him energetic and skilled in warfare - who had personally helped the Lindisfarne monks clear the Durham site a decade earlier and had married the bishop's daughter. The settlement was, in a real sense, his. When the siege began, his father was too old to fight, and Aelfhelm, Earl of York, refused to send aid. Uhtred raised a force from the lands of Bernicia and York on his own initiative and marched it to the Wear. The battle that followed was decisive. The Annals of Ulster recorded a slaughter of the good men of Scotland, suggesting that Scottish nobles fell in numbers. Malcolm withdrew north.

Tradition holds that local women were paid a cow each to clean the heads of the fallen Scottish attackers before those heads were mounted on spikes along the town's stockade. The detail is grim and probably embellished by later chroniclers, but it captures something true about the 11th-century borderlands - victory was a public display, and the bodies of the defeated were part of the message. Aethelred took notice of Uhtred. The king recognised him as earl while his father was still living, an unusual move, and when Aelfhelm of York died not long after, Aethelred granted Uhtred that earldom too. For the first time, Bernicia and Yorkshire were united under a single Northumbrian lord.

Uhtred's victory did not end the question of the northern border - it just postponed it. Malcolm came back in 1018, twelve years later, and won the Battle of Carham. After that, the lands north of the River Tweed were formally Scottish, where they remain. The siege of 1006 belongs to an older moment, when the boundary was still being argued in arrows and burned villages, when a town defended by monks and a young earl's improvised army could decide which crown a region paid taxes to. Durham would go on to build the Norman cathedral that still dominates the wooded loop of the Wear, but the medieval city sits on the same hill the monks chose in 995 - the hill Uhtred helped clear, the hill Malcolm tried and failed to take.