“”Overall, for cards issued both in the UK and elsewhere … 51.2 million Visa transactions were initiated and sent to Visa’s European systems for processing,” wrote Visa Europe chief executive Charlotte Hogg. “Of these, 5.2 million failed to process correctly,” she added in the letter to Treasury Select Committee chair Nicky Morgan. The outage was caused by a “very rare partial failure” of a switch in one of Visa’s data centres, Hogg added. It has since been fixed. Visa said there were 27.6 million transactions made in the UK during the disruption, of which 2.4 million failed to process properly.”