That could bring the British treasury around £5 billion ($7.8 billion). But Nicholas Shaxson, author of “Treasure Islands”, a book on offshore finance (and a former contributor to this paper), calls it a “Swiss tax swizz”: the country will in effect pay a fat fee to avoid revealing clients’ names. That undermines efforts at the Organisation for Economic Co-operation and Development, a Paris-based club of mostly rich countries, to set international standards on tax evasion.

Global Financial Integrity, a campaigning group, says poor countries “lose” more than $1 trillion a year to tax havens, around ten times the aid they receive. Two-thirds of this is tax evasion and avoidance, the group says, the rest transfers by criminals and the corrupt. Another outfit of fiscal inquisitors, the Tax Justice Network (TJN), cites research by the Bank for International Settlements, the Boston Consulting Group and McKinsey to calculate that global offshore deposits amount to at least $9 trillion, some $2 trillion more than the total held at home by American banks. ActionAid, a charity, published research this week showing that the companies in the FTSE 100 index had 8,492 offshore subsidiaries.

Campaigners also want to see more countries agree to the automatic exchange of tax information on non-residents. Bilateral tax treaties normally require such exchanges only on request. This works if the government seeking information knows precisely what it is looking for and if the host government can obtain it. As this issue has moved up policymakers’ agendas, some havens have voluntarily become more co-operative. The Isle of Man, for instance, now automatically swaps information (though Jersey refuses to follow suit for fear of losing “competitive advantage”).

Overall, however, resistance to change remains strong, not least in big Western financial centre's such as Wall Street and in the City of London, which see the flexibility offered by tax havens as an essential part of their business model. Public discontent may be filling the campaigners’ sails, but political support for reforms is still patchy. France, which holds the presidency of the Group of 20 (a club of the world’s biggest economies) wants to discuss tax havens at next month’s meeting in Cannes. But other countries are less keen, and more urgent items crowd the agenda.