This is probably the site of Billerwell Castle or Tower. In 1858 the OS describe it as ‘An old established name given to a small but prominent hillock situated about sixteen chains to the South side of Billerwell’. The OS site is not specifically marked, and the likely position of any tower is on the NE end of rising ground that terminates in a spur or ridge aligned NE/SW above the Billerwell farm access road, about 100 yards short of the farm cottages. The site is raised on three sides 15 metres above the surrounding ground. To the NW is the burn, to the SE is the road and good views across to Old Fodderlie. The ridge rises gradually to the West, but this is broken by a form of ditch cutting across the eminence. There are no traces of any structure and there are clear signs of quarrying or stone robbing; it is not possible to discern any pattern of foundation. The narrow neck on which the building stood would have limited its size to a maximum dimension of 20m by 30m. A later settlement called Birkhill was established in the mid-18th C, a little further to the SW, and is on Mathew Stobie’s map of 1770. The alignment of the three marked building fits the orientation of the site. The footings of these cottages could be the banks to the NW end of the knoll. Billerwell is listed as one of the earlier Estates or Barony’s in Rulewater and would merit a house of some size or strength. Pont and Bleau mark it on the same side of the Rule as the Tower Knowe. The 1947 OS map also marks the area as ‘Tower Knowe’. The farmhouse itself is some distance further down the track and dates from the mid-19th C.