The reason? The decision by the EU to back the introduction by 11 Eurozone countries of a Financial Transaction Tax. The original memo from the EU, which is in the form of an FAQ, can be found here, and full details of the Commission's proposals can be found here.
One of the most amusing features of the proposals is the "residency principle". I quote:
"This means that the tax will be due if any party to the transaction is established in a participating Member State, regardless of where the transaction takes place. This is the case both if a financial institution engaged in the transaction is, itself, established in the FTT-zone, or if it is acting on behalf of a party established in that jurisdiction."