A new era has begun for the United Kingdom after it completed its formal separation from the European Union.
The UK stopped following EU rules at 23:00 GMT, as replacement arrangements for travel, trade, immigration and security co-operation came into force.
Boris Johnson said the UK had “freedom in our hands” and the ability to do things “differently and better” now the long Brexit process was over.
But opponents of leaving the EU maintain the country will be worse off.
Scottish First Minister Nicola Sturgeon, whose ambition it is to take an independent Scotland back into the EU, tweeted: “Scotland will be back soon, Europe. Keep the light on.”
BBC Europe editor Katya Adler said there was a sense of relief in Brussels that the Brexit process was over, “but there is regret still at Brexit itself”.
The first lorries arriving at the border entered the UK without delay, while the first ferries have now left Dover for Calais.
UK ministers have warned there will be some disruption in the coming days and weeks, as new rules bed in and British firms trading with the continent come to terms with the changes.
But officials have insisted new border systems are “ready to go”.
As the first customs checks were completed after midnight, Eurotunnel spokesman John Keefe said: “It all went fine, everything’s running just as it was before 11pm. It’s very, very quiet, there are very few trucks around, as we predicted.”
The first ferry from Holyhead in Wales arrived in Dublin Port at 05:55 GMT with about a dozen lorries on board, all of which cleared customs checks for the first time without delays.
The UK officially left the 27-member political and economic bloc on 31 January, three and half years after the UK public voted to leave in the 2016 Brexit referendum.
But it has stuck to the EU’s trading rules for the past 11 months while the two sides negotiated their future economic partnership.