International regulators and politicians have been quick to take credit for forging international agreements to bring tax evaders to book over 15 years. But industry experts say action by whistleblowers and the theft of confidential information from banks has done far more in the past two years to prompt tax evaders into voluntary disclosures.

The Group of 20 leading nations proclaimed in April 2009: "The era of banking secrecy is over." It gave the Organisation for Economic Co-operation and Development the task of prising open the vaults of banks worldwide to reveal assets that have evaded the taxman. And tens of billions of dollars, euros and pounds have subsequently flowed into government coffers.