The vulnerability to internal erosion of a 100-year old typical British embankment dam without filters has been examined using seven methods. Four assessed the potential of the shoulder fill, a low permeability till, to act as a filter and prevent erosion through the core. These were the Sherard grading criteria, the Vaughan permeability criteria, the Delgado permeability criteria, and the Foster & Fell probability-based criterion. Two methods, particularly Fry’s, assessed whether sufficient tractive forces would be available to initiate and continue erosion. The seventh was the Interim Guide to Quantitative Risk Assessment for UK Reservoirs, which by comparing the characteristics and performance of the subject dam to that of similar embankment dams makes it possible to assess the probability of failure and whether this is acceptably low.