In practical terms, little has changed tonight. Businesses and citizens here will not feel any real difference in the coming weeks and months as they interact with the EU. But in another sense, everything has changed tonight.
The UK is now out of the EU and the bar for rejoining will be very high. First of all, a party would have to win an election on a rejoin platform and then, probably, have a referendum. It is hard to imagine a party serious about winning office choosing to reopen this issue in the foreseeable future. Second, there would have to be a national consensus in favour of rejoining. The EU would be reluctant to readmit Britain if it feared that it could want to come out again after the next election.
Attention will now shift to what terms the UK will leave on at the end of the transition period, more on that tomorrow. But this evening it is worth reflecting on the size of the change that has occurred. If you had said a decade ago that Britain would leave the EU in 2020, few would have agreed with you. But Britain now has. What this country must now demonstrate is the benefits of sovereignty, the advantages that can be gained from being able to make your own decisions on a host of issues.