The answer shows the close link between tax avoidance and the speculation that has fuelled financial instability for 30 years. There were clearly other causes of the current crisis but the faults of the international tax system were a big contributory factor.

International tax co-ordination depends on treaties based on a model devised 80 years ago. To prevent double taxation, the treaties generally give governments the right to tax returns from an investment in the investor’s country of residence. Business profits, meanwhile, are taxable in the “source” country where the activity takes place.

But for most of the past century, international investment was dominated by multinational corporations, which could choose the location of their sources of funds and organise their affiliates’ capital structures. This enabled them to devise techniques to ensure that they were not taxed unfairly, as they saw it, exploiting ambiguities in the concepts of residence and source using legal entities formed in convenient jurisdictions. Such methods were also pioneered, with rather less legitimacy, by wealthy people resentful of high income taxes.

The relaxation and final abandonment of exchange controls in the 1970s led to the blossoming of “offshore” finance and a boom in tax havens. These depend on both outright tax evasion and the exploitation of grey areas by tax avoidance. Since large multinationals are as much financial as business entities, they have freedom to devise complex financial structures – financial institutions, such as banks, even more so: in recent separate surveys by the US Government Accountability Office and the Tax Justice Network, the largest user of tax havens in every country surveyed was a bank. Tax authorities have enormous problems puzzling out these structures. If they can, it is often hard to characterise them as shams.

The leading countries themselves are also host to major financial centres, from which most of these activities are directed. The revenue authorities in these countries, not least the US and the UK, have been cowed into accepting these activities for fear of losing finance business.

Take hedge funds, for example. The tax authorities in the US and the UK have accepted a lax interpretation of residence and source rules, accepting that these funds are resident and their profits sourced offshore (mostly in the Cayman Islands) – even though they are effectively managed from London and New York. Not only are the funds’ gains treated as realised in Cayman, and hence not taxable, but their distributions are not subject to withholding tax – a great benefit for their investors. The funds’ location in a secrecy jurisdiction facilitates tax avoidance and is an open invitation to evasion.

For multinationals and rich investors the point is the same: returns on financial transactions are ultimately taxed at a low or zero rate, making them far more profitable than genuine business endeavours. This distortion of the tax system has greatly fuelled the excess of liquidity channelled into largely speculative financial transactions. The offshore secrecy system has been a main element of the opacity that has undermined corporate and financial regulation.

In support of his assertion that waterboarding is not torture, the Taliban commander cited legal analysis produced by the Office of Legal Counsel of the U.S. Department of Justice. He pointed out that the authors of this legal analysis are a respected federal judge on the second highest court in America and a professor at a top American law school. The Taliban commander also referred to the careful legal analysis of a Distinguished Professor of Law who concluded that waterboarding is not torture because U.S. trainers did it to their own troops "hundreds and hundreds of times."