I t happened again. A power outage hit a datacentre in London , and things cascaded from there: multiple banking services faltered, court hearings were put on hold and patients reported temporary glitches on the NHS app.

The datacentre in question was in Google’s europe-west2-b zone, one of more than a dozen “zones” that the US search giant maintains in Europe to service its clients.

The outages – which have affected, according to the website Downdetector, Royal Mail, Revolut, HSBC and Lloyds bank, among others, are so far not of the scale of a similar cascade this time last year, when Amazon Web Services went down for nearly half a day.

That outage hit a far bigger node – Amazon’s us-east-1 – in a concentrated region of Virginia, which hosts the greatest density of datacentres on Earth.…