It is widely expected that the European Commission’s antitrust commissioner Joaquín Almunia will next Wednesday formally block the merger between NYSE Euronext and Deutsche Börse, nearly a year after the exchanges first announced the deal.

This leaves a dilemma for the two exchanges. In the coming days, they will have to decide whether or not to pursue the matter to the bitter end and await the Commission's formal judgement - or withdraw their notification and voluntarily terminate the deal.