Both sides responded to the challenge of the conflict by building many new castles, sometimes as sets of strategic fortifications. In the south-west Matilda's supporters built a range of castles to protect the territory, usually motte and bailey designs such as those at Winchcombe, Upper Slaughter, or Bampton. Similarly, Stephen built a new chain of fen-edge castles at Burwell, Lidgate, Rampton, Caxton, and Swavesey – all about six to nine miles (10–15 km) apart – in order to protect his lands around Cambridge. Many of these castles were termed "adulterine" (unauthorised), because no formal permission was given for their construction. Contemporary chroniclers saw this as a matter of concern; Robert of Torigny suggested that as many as 1,115 such castles had been built during the conflict, although this was probably an exaggeration as elsewhere he suggests an alternative figure of 126. Another feature of the war was the creation of many "counter-castles". These had been used in English conflicts for several years before the civil war and involved building a basic castle during a siege, alongside the main target of attack. Typically these would be built in either a ringwork or a motte-and-bailey design between 200 and 300 yards (180 and 270 metres) away from the target, just beyond the range of a bow. Counter-castles could be used to either act as firing platforms for siege weaponry, or as bases for controlling the region in their own right. Most counter-castles were destroyed after their use but in some cases the earthworks survived, such as the counter-castles called Jew's Mount and Mount Pelham built by Stephen in 1141 outside Oxford Castle.