There has been a multi-tier Europe since 1993 when Denmark received optouts from the euro, judicial-cooperation, European citizenship and the Common Foreign and Security Policy. Since then, Ireland and the UK have remained outside of the Schengen Agreement (abolishing internal border-controls) while Ireland has an optin on an ad hoc basis on common policies in the area of Justice and Home Affairs. So when the elite warn of a "two-speed/tier Europe", they are warning of something that has been there for 16 years.
