progressed well, and historian David Crouch describes it as "a military achievement of the first rank". The King took the opportunity of his military advantage to forge a peace agreement with Scotland. Stephen's wife Matilda was sent to negotiate another agreement between Stephen and David, called the treaty of Durham; Northumbria and Cumbria would effectively be granted to David and his son Henry, in exchange for their fealty and future peace along the border. Unfortunately, the powerful Ranulf I, Earl of Chester, considered himself to hold the traditional rights to Carlisle and Cumberland and was extremely displeased to see them being given to the Scots. Nonetheless, Stephen could now focus his attention on the anticipated invasion of England by Robert and Matilda's forces. Road to civil war (1139) Stephen prepared for the Angevin invasion by creating a number of additional earldoms. Only a handful of earldoms had existed under Henry I and these had been largely symbolic in nature. Stephen created many more, filling them with men he considered to be loyal, capable military commanders, and in the more vulnerable parts of the country assigning them new lands and additional executive powers. He appears to have had several objectives in mind, including both ensuring the loyalty of his key supporters by granting them these honours, and improving his defences in key parts of the kingdom. Stephen was heavily influenced by his principal advisor, Waleran de Beaumont, the twin brother of Robert of Leicester. The Beaumont twins and their younger brother and cousins received the majority of these new earldoms. From 1138 onwards, Stephen gave them the earldoms of Worcester, Leicester, Hereford, Warwick and Pembroke, which – especially when combined with the possessions of Stephen's new ally, Prince Henry, in Cumberland and Northumbria – created a wide block of territory to act as a buffer zone between the troubled south-west, Chester, and the rest of the kingdom. With their new lands, the power of the Beamounts grew to the point where David Crouch suggests that it became "dangerous to be anything other than a friend of Waleran" at Stephen's court. Stephen took steps to remove a group of bishops he regarded as a threat to his rule. The royal administration under Henry I had been headed by Roger, Bishop of Salisbury, who was supported by his nephews, Bishops Alexander of Lincoln and Nigel of Ely, and his son, Lord Chancellor Roger