Bernard Madoff, the mastermind of the biggest “Ponzi” scheme in history, told inspectors in a June interview that it was “amazing” to him that he was never caught during investigations by the US Securities and Exchange Commission.

On June 17, 12 days before he was sentenced to 150 years in prison, Mr Madoff sat down with David Kotz, the agency’s internal watchdog, and Noelle Frangipane, his deputy, and described to them how shocked he was in 2006 when investigators nearly figured him out but failed to do basic due diligence such as checking with the Depository Trust and Clearing Corp to verify his trades.