After three years of uncertainty, political acrimony and fractured opinions across a nation that found itself divided as never before, Brexit finally arrived on Friday night.

At 11 p.m. — midnight in Brussels — Britain said farewell to the European Union, officially departing from the bloc after 47 years of membership and setting off on a new solo journey. While the moment was highly anticipated in the years since the country’s 2016 referendum, little will immediately change when the countdown is over.

The commemorations have been notably subdued. Even the official government celebrations — a victory lap for Prime Minister Boris Johnson, who had pledged to see through Britain’s withdrawal from the European Union “do or die” — were muted. British flags lined the square outside Parliament and the Mall leading to Buckingham Palace, and a light show was staged outside Mr. Johnson’s official residence in Downing Street, a side road that is closed to the public.

Elsewhere, those who supported remaining in the European Union staged protests and others wore mourning clothes to show their grief at the end of Britain’s membership.