From London to Lyons, this week has given many people their first sharp taste of winter. Adding to the chill is the prospect of bigger bills as heat and power prices soar to vertiginous levels. In all the main economic regions of the globe, energy systems are heavily stretched in the attempt to meet ever-increasing demand.

Could an unusually cold winter be the trigger that tests one of those systems to the limit – and perhaps beyond? And does the absence of slack in the system mean that even a relatively warm winter could cause serious disruption to supplies?