By late afternoon on Tuesday, only six of Revolut's 27 listed services were working. Among those still running were support chat and internal transfers, which was little comfort to a customer standing at a cash machine that would not pay out. The cause was not a cyberattack or a software bug in the bank's own code. It was a "power event" in one zone of Google's cloud operations in London, known as europe-west2-b.

The damage spread well beyond one app. Lloyds and HSBC customers reported trouble with online services, and Halifax, which Lloyds owns, said some users could not log in. Revolut said its sign-up, card payments, transfers, ATM withdrawals and cryptocurrency services were all affected, while insisting that customers' money and data were safe. Meanwhile, the video system that lets defendants, lawyers and other parties join hearings remotely across England and Wales failed throughout the morning.

Because it is often used for defendants in custody, several hearings were believed to have been delayed. Google said services began returning at 1pm and were back for most customers by 3pm. The significance lies in what the outage reveals about hidden dependencies. Institutions that compete fiercely, or that have nothing in common, turned out to rest on the same physical infrastructure.