are you really suggesting that the army of safety analysists at NATS do not understand the concept of risk?
I am not sure 'not understand' is true. However NATS/UK CAA/HAL do seem to have a different perception of risk management than most of the rest of the world. Not necessarily wrong ... but different.
This is true in a number of different aspects of operations not just the recent ash. And interestingly is not always more risk adverse (think of IFR OCAS with no service - 'normal' practice UK, not really done anywhere else - but not NATS' problem if anything goes wrong!)