Cascading failure

The National Risk Register 2025 uses "cascading" in two of its risk descriptions, and both uses describe one failure setting off others. Its scenario for the loss of position, navigation and timing services says those signals are "essential for telecommunications, transport navigation and providing precise timings", and that losing them "would have catastrophic and cascading effects across the UK and globally". Its scenario for a national electricity failure lists "cascading technical failures" alongside an extreme weather event and a cyber attack among the possible causes.

The power failure scenario is the register's clearest picture of the cascade itself. It assumes a total failure of the National Electricity Transmission System, so that all consumers without backup generators lose their mains supply "instantaneously and without warning". A nationwide loss of power "would result in secondary impacts across critical utilities networks (including mobile and internet telecommunications, water, sewage, fuel and gas)", causing significant and widespread disruption to public services, businesses and households, and loss of life.

The register's method is built for this. It says the government plans against "common consequences of risks", such as disruption to a range of critical services, so that generic capabilities can be used "regardless of the risk that caused them".