An electrical substation fire and an entire airport shut down - with over 1,000 flights cancelled, others rerouted worldwide, and 200,000 passengers affected by the disruption. The Heathrow closure on Friday really highlights the 'critical' part of critical national infrastructure (CNI) - the systems and facilities that are essential for society to function. At best it's an embarrassment. At worst, it points to serious vulnerabilities across the country that could be exploited by bad actors. Heathrow first. Heathrow needs a lot of power, the equivalent of a small town, and the bulk of this is supplied by a dedicated connection...