Johnson's Conservatives increased their share of the vote to 43.6 percent, their highest since Thatcher's first election victory in 1979, and higher than Blair's in any of his three election wins.
Several hundred protesters marched through central London on Friday to protest against Britain's election result, chanting "Boris Johnson: Not My Prime Minister" and "Boris, Boris, Boris: Out, Out, Out".
The protesters, brandishing signs that read "Defy Tory (Conservative) Rule" and "Refugees Welcome", walked at speed from outside Johnson's Downing Street residence to Trafalgar Square and on to the theater district, blocking traffic and drawing a heavy police presence.
Johnson's Conservatives won Thursday's election by a large margin. On Friday he called for "closure" over the Brexit divisions that have riven the United Kingdom for the past three and a half years.
Johnson, the face of the victorious "Leave" campaign in the 2016 referendum, fought the election under the slogan of "Get Brexit Done", promising to end the deadlock and spend more on health, education and the police.
He was vindicated with the biggest Conservative win since Margaret Thatcher's landslide victory of 1987, trouncing his socialist Labour Party opponent Jeremy Corbyn by winning 365 seats with a majority of 80. Labour won 203 seats.
President Donald Trump congratulated Johnson and said a U.S. trade deal could be more lucrative than any with the EU, the world's biggest trading bloc. "Celebrate Boris!" Trump said on Twitter.