LSE Law Brexit special #2: the constitutional context to triggering Article 50 TEU

The mythical Art.50 TEU gives Member States the option to withdraw from the EU ‘in accordance with its own constitutional requirements’. But what are the constitutional requirements of a country with no written constitution? And which institution is best placed to resolve the competing constitutional claims regarding prerogative powers, Acts of Parliament, conventions, and individual rights that were voiced by the government, the devolved administrations, and by the claimants?