Carlisle Castle was first built during the reign of William II of England, the son of William the Conqueror who invaded England in 1066. At that time, Cumberland (the original name for north and west Cumbria) was still considered a part of Scotland. William II ordered the construction of a Norman style motte and bailey castle in Carlisle on the site of an old Roman fort, with construction beginning in 1093. The need for a castle in Carlisle was to keep the northern border of England secured against the threat of invasion from Scotland. In 1122, Henry I of England ordered a stone castle to be constructed on the site. Thus a keep and city walls were constructed. The existing Keep dates from somewhere between 1122 and 1135.