The Treasury is poised to announce new rules for Britain's big banks this coming week. A major shake-up of the ring-fencing regime is expected, in an effort to safeguard depositors at Britain's largest retail banks, as ministers rush to stimulate economic growth. According to Sky News reports, Chancellor Rachel Reeves has approved proposals designed to release billions of pounds of extra lending capacity at five high street banking giants. Barclays, HSBC, Lloyds Banking Group, NatWest and