The Panama Papers are an unprecedented leak of 11.5m files from the database of the world’s fourth biggest offshore law firm, Mossack Fonseca...The documents show the myriad ways in which the rich can exploit secretive offshore tax regimes. Twelve national leaders are among 143 politicians, their families and close associates from around the world known to have been using offshore tax havens...Are all people who use offshore structures crooks?  No. Using offshore structures is entirely legal. There are many legitimate reasons for doing so...Are some people who use offshore structures crooks? Yes. In a speech last year in Singapore, David Cameron said “the corrupt, criminals and money launderers” take advantage of anonymous company structures. The government is trying to do something about this. It wants to set up a central register that will reveal the beneficial owners of offshore companies. From June, UK companies will have to reveal their “significant” owners for the first time...What does Mossack Fonseca say about the leak?  The firm won’t discuss specific cases of alleged wrongdoing, citing client confidentiality. But it robustly defends its conduct...