Notes on the UK Non-Native Organism Risk Assessment Scheme
  In 2004, the UK Government's Department for Environment, Food and Rural Affairs commissioned research with the aim of developing a scheme for assessing the risks posed to species, habitats and ecosystems in the UK by non-native organisms. The outcome was the UK Non-Native Organism Risk Assessment Scheme. Unfortunately, the mathematical basis of the procedure for summarising risks deployed in the Risk Assessment Scheme, as outlined in Baker et al. (2008) and described in more detail in the Risk Assessment Scheme's User Manual, contains several analytical errors. These errors are outlined in the notes that follow. 
Gareth Hughes