Visa's ten-hour outage across Europe at the start of this month caused more than five million transactions to fail, the company has told a UK select committee. In a written response, Visa's European boss Charlotte Hogg told the committee that a component (elsewhere reported as "a broken switch") in Visa's primary data centre "suffered a very rare partial failure", reports Finextra. This meant Visa's secondary data centre was not able to kick in properly and automatically process all transactions. "The malfunctioning system at the primary data centre continued to try to synchronise messages with the secondary site. This created a backlog of messages at the secondary data centre which, in turn, slowed down that site's ability to process incoming transactions," Hogg wrote. Visa said steps had been taken to reduce the chances of a repeat failure and it would migrate European processing to its global VisaNet system which it describes as more resilient.