In 2013 contractors re-discovered a native Crayfish population on a National Trust site in Surrey. In October 2014 the National Trust commissioned a survey of their property and the catchment upstream. Following several visits to the site and adjacent properties we found that White-claw Crayfish were still surviving along a 3km stretch of water-way. However, this remnant population is under serious threat with Signal populations close by and an active angling society presenting a potential biosecurity issue. A dam on site provides some protection to signal spread and it is hoped that a biosecurity workshop with interest groups will help.