The fallout will be enormous. Journalists from 78 countries have begun publishing stories on the hidden wealth of politicians and celebrities, based on a leak of 11.5m files from the database of Mossack Fonseca, a Panamanian law firm. These contain details of offshore shell companies and the like (the British Virgin Islands has been the most popular domicile) and of activities ranging from the benign to the alleged looting of public wealth. Among those with links to the accounts’ owners are Russia’s president, Vladimir Putin, and his Chinese counterpart, Xi Jinping. Iceland’s prime minister is under pressure to resign: the files show he sold his 50% stake in Wintris, an undeclared offshore company, to his wife for $1. Several countries, including Sweden and Australia, have opened investigations. An anti-corruption summit in London in May was already due to discuss financial secrecy. It could hardly be more topical.