So-called Open Banking kicks off on Saturday in what amounts to a gigantic financial experiment in which Britain is leading the world. Under the scheme, 9 of the biggest lenders in the UK - Lloyds, RBS, Barclays, HSBC, Santander, Danske, Allied Irish Bank, Bank of Ireland and Nationwide Building Society - must open the information they hold on the transactions history of their customer, should that customer give their permission.