Prime Minister Boris Johnson hailed an “astonishing moment” as Britain formally left the European Union (EU) after 47 years on Friday.
He stated that his government “obeyed the people” who voted for Brexit in a 2016 referendum.
UK is the first country to leave the bloc.
On Thursday, EU member states gave their final formal go-ahead for Britain’s departure from the bloc.
“For many people this is an astonishing moment of hope, a moment they thought would never come,” Johnson said in a speech broadcast via his Facebook.
“And there are many of course who feel a sense of anxiety and loss.
“And then of course there is a third group – perhaps the biggest – who had started to worry that the whole political wrangle would never come to an end.
“We have obeyed the people [who voted for Brexit in a 2016 referendum,” he said, adding: “We have taken back the tools of self-government.”
Dpa quoted German Chancellor Angela Merkel as saying Brexit was a “deep cut for us all”.
“A historic alarm signal that must sound in all our countries, that must be heard by all of Europe and make us reflect,” French President Emmanuel Macron said.