When the Lisbon Treaty was signed in 2007, the inclusion of Article 50 was hailed as a concession to British Eurosceptics. For the first time there was an exit clause: a clear, legal way for a country to leave the European Union. Whatever concerns Britain had about the federalist direction of the EU, it was now at least enshrined in treaty that this country had a right to get out should MPs vote for it to do so.