The decision in 2004 by Tony Blair’s New Labour government to allow unfettered access to the UK for citizens of the 8 central and east European EU newcomers has had monumentally important implications. Most other member states imposed transitional restrictions of up to 7 years. If Britain had done so too then it’s probably safe to say that the scale of movement to Britain would have been tiny in comparison with actual numbers and Britain would still be in the EU.
If about one thing, the 2016 referendum was about immigration, but British immigration politics are broken. While strained at times, it once was that a two party Con-Lab consensus established in the 1960s removed the issue from wider public debate. This consensus has long since been stretched way beyond breaking point fuelled not least by the steep growth in migration from other EU members after 2004.