Earlier quoted context omitted.
Jump down to the Cause section. Millions of high-powered electric kettles being switched on during a popular show's break.
But why is that unique to the UK? Plenty of other cultures use electric kettles and follow soaps. (Also did streaming dent the effect?)
For much of my childhood there were only four (and briefly before the boom, five) TV channels. Major events like football would have a significant proportion of UK households all watching, and in those breaks a signficiant fraction would switch on an extra 1.5-2 kW device.
If the average household was four people, and 50% of households used a kettle in the same ad break, that would've been a surge of around 60e6*0.25*0.5*2kW = 15 GW in a nation whose mean load is about 40 GW.