HSBC's Swiss banking arm helped wealthy customers dodge taxes and conceal millions of dollars of assets, doling out bundles of untraceable cash and advising clients on how to circumvent domestic tax authorities, according to a huge cache of leaked secret bank account files. HSBC was headed during the period covered in the files by Stephen Green - now Lord Green - who served as the global bank's chief executive, then group chairman until 2010 when he left to become a trade minister in the House of Lords for David Cameron's new government. The files show how HSBC in Switzerland keenly marketed tax avoidance strategies to its wealthy clients. The bank proactively contacted clients in 2005 to suggest ways to avoid a new tax levied on the Swiss savings accounts of EU citizens, a measure brought in through a treaty between Switzerland and the EU to tackle secret offshore accounts. The documents also show HSBC's Swiss subsidiary providing banking services to relatives of dictators, people implicated in African corruption scandals, arms industry figures and others. HSBC is already facing criminal investigations and charges in France, Belgium, the US and Argentina as a result of the leak of the files, but no legal action has been taken against it in Britain.