 He was soon faced with a political challenge to the independence of his church . The challenge came from the English church , and was not new , but had lain dormant for some decades . The reason it was awakened was that in the summer of 1174 King William had invaded northern England , and on 13 July , having been caught underprotected during a siege at Alnwick , was captured and taken into English custody . The capture was disastrous for the king , leading to a revolt by Gilla Brigte , Lord of Galloway , and to many of William 's discontented subjects " ruthlessly " slaying " their English and French neighbours " and perpetrating a " most wretched and widespread persecution of the English both in Scotland and Galloway " , that is , of the English and French @-@ speaking settlers William and his predecessors had planted around the castles and towns of his Gaelic @-@ speaking territories in order to increase royal authority . Worse still , and more significantly for Jocelin , in the following year King Henry II of England forced William to sign the Treaty of Falaise , a treaty which made William Henry 's vassal specifically for Scotland and sanctioned the subordination of the kingdom 's bishoprics to the English church . 
