The IMF have just released another paper on the Robin Hood Tax, focused solely on exploring the administrative practicability of a Financial Transaction Tax (FTT).
Their conclusion? "In principle, an FTT is no more difficult, and in some respects easier, to administer than other taxes". Furthermore, they recognise that whilst international agreement enhances the viability of an FTT, several countries have successfully introduced them on a unilateral basis. The need for international agreement cannot be used as an excuse to prevent European countries, including the UK, from pressing ahead.
But perhaps the most interesting thing about the paper is the subtle change it suggests in the terms of the debate: the paper does not consider whether an FTT should be applied, but instead how it should be applied. That's a welcome development.