“If Mastercard and Visa were turned off, it would send us back to the 1950s,” before cards dominated the UK economy, and businesses wholly relied on cash, one executive familiar with the project told the Guardian. “Of course, we need a sovereign payments system.”

The potential disruption could be vast. In Russia, where businesses are reliant on Visa and Mastercard for 60% of payments, US sanctions that forced the companies to turn off their services left ordinary people stranded without access to funds and unable to buy goods.

Similar concerns are being raised in the EU, where politicians have taken a vocal stance on building locally owned networks that could not be turned off on a whim by foreign powers. The chair of the European parliament’s economic and monetary affairs committee, Aurore Lalucq, issued a stark warning that went viral last month about relying on US companies for such an essential service.

“Visa, Mastercard … the urgent issue is our payment system. Trump can cut everything off,” Lalucq said. “The rest is poetry. I urgently request that the commission organise a European Airbus for payment systems: you can’t say you weren’t warned.”