When the Norman conquerors arrived in England in 1066 the Kingdom of Northumbria was already a distant memory. Yorkshire, once an important part of Northumbria had fallen to the Vikings two hundred years earlier and it too had been incorporated into England well before William the Conqueror arrived.

Northumbria lived on only as a depleted earldom stretching from the Tees to the mouth of the Tweed. The Earldom of Northumbria encompassed what would become the counties of Durham and Northumberland and it was the Normans who divided this region into these two parts. In the south the County Palatinate of Durham was created while the remainder of Northumbria north of the Tyne came to be known as Northumberland.

The Norman Prince Bishops ruled the roost in Durham and they were expected to defend their land from the Scots. Their great castle at Durham was their principal fortification, but as Sir Walter Scott later noted Durham Cathedral was itself "half church of god, half castle against the Scot". In Northumberland the defensive role fell upon an assortment of powerful war hungry barons and landowners who inhabited solidly defended castles.

After the death of the Scottish king, Malcolm Canmore, in battle at Alnwick in 1093, Norman influence in Scotland became increasingly significant. One of Malcolm's sons, David I, who became King of Scotland in 1124 had been educated at the Norman court in England and invited many Norman landowners to settle in lowland Scotland. Amongst them was a family called De Brus (Bruce) who held land in North Yorkshire and Hartlepool.

In addition to his Norman connections David had strong family ties with the old earls of Northumbria that gave him strong reasons to claim North East England as his own. In 1138 he invaded the north in an attempt to annex the region and on August 22, a battle ensued at Northallerton (the Battle of the Standard) between the English and the Scots. The English forces were composed almost entirely of Yorkshire barons led by Thurstan, the Archbishop of York who was once a close friend of David. David's army was heavily defeated in the battle and he was forced to retreat to his castle at Carlisle.

Despite David's defeat, the Scottish king's claim to North East England was given some serious consideration by Stephen the King of England. Finally at Durham City on April 9 1139, a peace treaty was signed in which most of the region was given to King David's son, Henry. Bamburgh Castle, Newcastle castle, Stockton, Darlington and the parts of Durham then belonging to the Prince Bishops were not part of the deal, but the River Tees effectively became the Scottish border.

Two years later the Scottish control of the North East was virtually complete when King David's Chancellor, William Cumin illegally appointed himself the Prince Bishop of Durham following the death of the previous bishop. Cumin's hold was however short lived. The usurper was eventually ousted in 1144. David passed away in 1153. His son, Henry had died the previous year. The North East passed to the new Scottish king Malcolm IV who held onto the region until 1157 when a new and powerful King of England, Henry II reclaimed the land. Nevertheless for eighteen years the North East had been virtually a part of Scotland.

Scottish claims to the region continued for many decades and the region was under constant threat of invasion from the north. Some kings and raiders saw the region merely as a source of plunder. As time passed many grand castles and hundreds of lesser fortifications called pele towers (pronounced peel) would be built across the North East in the centuries to come. Indeed Northumberland has more castles than any other part of England.

Pele towers were lived in by rich and poor alike and were virtually impregnable against raiders and marauders.